Don't let the service intervals scare you. Valve adjustments have proven to be easy and not nearly as frequent as suggested. Many people have checked their valve clearances at 150 hours and found that they have not moved a single millimeter. As for the oil changes, most guys change the engine side twice as frequently as the gearbox. The engine side holds 600ml (yes, just over half of a litre), oil filters are commonly changed every other oil change and they're only $7.00. The entire oil change takes literally ten minutes. If you're that concerned, get an HT Racing oil cooler and it adds 80% more oil capacity while cooling your oil very well - this is a well proven solution for many guys who have "adventurized" their small KTMs.
My next bike will likely be a 350 EXC-F mainly for use at places like Ganny and some dirt road exploration. Also will terrorise the streets from time-to-time. I've also wondered about the strict service intervals. I believe KTM's documentation is all based on the bikes being used for racing. Constantly being redlined and subjected to low speed, high load, high temperature enduro racing. For normal leisure riding, no way you would need to replace the piston and valve train every 135 hours.