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.