I posted this in a thread on Technical Know How but I think the point is so important that I'm re-posting it here as a new thread, with a couple of edits:
The idea of doing a "service" on a bike is misguided; it's not a modern car where you only need to change oils and filters and not much else. A bicycle is a collection of delicate lightweight systems that need to be tweaked and kept in adjustment to get the best from them and the only way to do that is to learn to do it yourself.
I despair when I see people posting that their bike "has just been serviced " and they expect it to be running perfectly. You will only know when a something needs attention if you are attuned to the sound and feel of it or you take the time to inspect it carefully; which you can't expect a mechanic in a bike shop to do when he's under pressure and being distracted by colleagues, customers, loud music and his mobile phone. Read Zen and the Art of Motorcycle Maintenance if you want to understand more about quality work and the futility of handing your precious machine to a so-called "professional".
Bike "servicing" is a dirty, boring, tiring, tedious job that makes no profit no matter how much the shop charges. Speaking as a bike fettler who has tried, briefly, to make a living from servicing bikes, there's nothing more depressing or demotivating than receiving a bike in a filthy or neglected condition from a customer who expects you to wave a magic wand and make it like new again, especially when you know that your efforts won't be appreciated and they will continue to abuse and neglect the bike.
The simplest and cheapest answer is to buy some tools and learn to do your own maintenance. That way, when the bike breaks out on the road, you've a better chance of fixing it yourself.
Not all bike mechanics are muppets; I know a couple of excellent mechanics at my LBSs who certainly know more than me but I would not expect them to be able to perform routine maintenance or adjustments, which is the rider's job.
