How important is it to regulalrly true wheels?

its just not necessary on well built wheels. frequent need of being trued up is a pretty solid sign of a poor wheel build.

id check your wheel tension, you can do the pluck spokes method (listen for similar tones from spokes on the same side).. if they're off, you should rebuild your wheel to proper tension.

wheels and spokes should be checked frequently, its not a bad idea to give it a quick run over before a ride, but constant tune ups of spokes shouldnt be necessary on good builds.

It depends especially what type of riding you do. According to Spesh Big Hit in your post I guess FR. Freeriding is sensitive for good material, so having a trued wheels will definitely increase their life time.

I'm there w/ one pivot. Well built wheels ridden by a good rider should hardly need a spoke wrench. On the other hand if your wheels are poorly built or if you ain't got no skills or some combination of the two....

They need to be checked frequently , good wheel builds rarely need to be trued as routine maintanance .

Get the wheel built right early on, meaning they're true and the tensions are somewhat equal all the way around. If they're built poorly and they come out of true, simply re-truing them will put the spoke tensions further out of whack, leading to them being more prone to coming out of true and eventually leading to needing new rims/spokes.

My wheels get put on the truing stand when I switch tires (they won't fit on it with tires anyway)...I rarely need to do much. I hand tensioned mine (OEM machine built wheels that came with the bike) when I assembled the bike, and since they were disc wheels I paid more attention to even tension then being slightly out of true (a mm or so makes no difference on disc with plenty of tire clearance).

Otherwise I eyeball them (not the tire!) when I clean and service my bike.

I am a larger guy and I used to bend rims on a regular basis!! And I am pretty particular about keeping my wheels true and spokes tight!