You just have to be sensible. It ain't rocket science. I adjust all my basses 2x a year (except my thumb bass with all wenge neck), once in the fall and once in the spring. The thumb is so stable, it never moves seasonally.
At $20 a setup we're talking a serious bi-annual payout!
I think a lot of people who are timid about doing their own setup are that way because they aren't sure what setup is right for them. There's a lot of different ways to do it, and each setup is a compromise. You simply can't have everything in your setup.
For example, you can't have your action super low, and keep every fret buzz free. It's all tradeoff, as the adjustments that keep all the frets from buzzing and keep the action low fight each other.
This is pretty over simplified, so let me distill my point:
Anyone with a shred of patience and the right tools can adjust their truss rod using any number of simple guides found online. BUT, you aren't just randomly twisting. You need to decide what setup works for you. If you are randomly turning screws and tweaking til it feels right, chances are you aren't gonna get anywhere fast. If you know the setup you want, and have learned to measure neck relief, it should be easy for you to make PURPOSEFUL adjustments and dial in your neck and bridge to your setup pretty quickly and easily.