Real world training for the time restrained?

May not be a popular option, but I spent a year riding pre-dawn anywhere from 12-25 miles a few weekday mornings, riding my mtn bike on the road (with some occasional trail riding). Every now and then I put in 40 miles (half road / half trail) on a weekend morning.
I threw some intervals in the mix as well, and tried to keep training from getting stale. I was realistic, shot for midpack results and got them (Swank 65, Heritage Park 6hr, Harbison xc, Cowbell marathon). I found I could easily wake up before my 5am alarm if I knew I was going to ride that morning.

Traffic for me was extremely scant. I had some beautiful scenery as the sun rose (giant Lake Murray dam in SC), and I could maintain all my other commitments: 2 kids under age 5, 45-60hr work weeks, evening commitments to juggle, etc.

It means an investment in decent lighting, but I haven't known too many riders to shy away from new gear. I relied on used NightRider Classic dual-beam handlebar lights, and a 10w HeadTrip helmet light on fleabay for ~ $110. A cheap safety vest didn't hurt either.

Food for thought.

Take advantage of the big commute by riding all or part of it a couple of times a week. You can be creative by leaving the car at work or halfway home after work, riding home then riding back the next day. Carpool one way and ride home too? This type of thing x2/week done at a steady moderate tempo pace will do a ton for endurance.

1 hour weekdays - you can get a lot done in an hour if you are doing intervals. With your endurance focus go heavy on the longer 6 - 20 min intervals.

Like this one:
High cadence tempo intervals. Warm up well then ride 5 X 6 minutes at 95+ rpm in power L4 (or near lactate threshold heart rate or power) with 2 minute very easy recoveries between each.

2-hour weekend rides - do these on the trails on the mtb and rally around hard on hilly terrain for 90 mins during that 2 hour ride. Have fun and hit the types of terrain you will race on.

1hr a night and 2hr weekend rides are perfect.
I have raced front of the pack with this much training for quite a few years. Not bragging just letting you know it is doable. I am very average in terms of genetic potential as determined by lab testing, so it's not like you need to be a genetic freak with massive VO2max to do well.

Intervals at VO2max as determined in Veronique Billat's peer reviewed publications will boost your lactate threshold and VO2max. This is important for any endurance racing (anything over 10mins of racing)

If you have some time read this http://www.pponline.co.uk/encyc/0600b.htm
can be applied to cycling just as easily. Believe me. I've been training like this for years and it works. I have two kids, a 3 year old and a 7month old. Time is not on my side.

Ok this is my mod of Billat's training. Determine your vVO2max. Your velocity at VO2max. Yes you will need to do this on a trainer and preferably with power meter.....you can just use your speedometer. Find your best average for 6mins.
Now you are read ride your intervals. 3mins at 90% vVO2 then 3mins off. Maintain similar cadence. ride the 3min off at around 50% vVO2max. Only do 5 intervals and that is it.
5x3/3 with 10min warm up and 5min cool down is 50mins.
This is really hard. I spend a few minutes before this session just getting in my head in the zone to perform the intervals at the right intensity and not give up before the last set.
You can alternate this interval set with 20x 30sec on, 30sec off. Hit the 30sec on at 110% vVO2max and the off at 75% vVO2max. This session is much easier mentally but should still have a very similar effect.
The key to these intervals is that you are trying to spend as much time as possible riding at your ventilatory threshold. It usually takes around a minute or sometimes two to reach this threshold, hence why you need to either have longer intervals (but not too long so that you fade and cannot hit the next one) or shorter intervals at higher intensity with less recovery.
Billat's research has shown that VO2 training in this way also has a huge effect on lactate threshold, which is what you need for endurance racing.
I try to hit these intervals 3x a week. Those other nights you have spare, just go ride your bike in your sweet spot (the power zone just below lactate threshold, i.e just before that first deepening of breath).
That 2hr weekend ride, just go out and have fun and smash the climbs. There's alot more to endurance racing than fitness, you need to train your brain to cope with the misery and sore contact points, feet, hands and of course back door. You can only do that by nailing the odd 6hr ride. That's when you find that tiny tweak you need to make to your cleat to stop that wee knee twinge that you don't really notice on shorter rides but turns into a deal breaker on longer stuff.
Don't forget to have fun. killer intervals can wreck your chi. 3x a week ok, don't try doing more, your will to live will be erased.
Hey just my two cents.

I've managed to do OK with three days a week of serious training, 40K road TT in about 56 minutes, finished trans iowa V3 in 30 hours, last year got my super randonneur pin. My deal is two weeknights of hard efforts and try for a long ride on one of the weekend days. My "hard" rides are either a 10 mile outdoor TT that I do a lot so can compare the times or a 25-26 minute computrainer ride (8 miles at a 2% grade). With a 5-10 minute warmup and cooldown we're talking less than 45 minutes. There area a lot of good ideas for hard efforts but I like the idea of "hard race pace for a total of 30-60 minutes per week"

I guess it's just that if you go hard Monday or tuesday night then recover for a couple of days then punch it thursday or friday night then a couple of days then a long one Saturday or Sunday then a day or two recovery....I'd like to have a "recovery" ride but when is a guy going to get that??