Really enjoying your site, what a nice piece of work! I found it while looking to answer the question of what I should do about my Schwinn CrissCross, a hybrid I bought 14 year ago. It's been ridden off an on throughout those years, but it's getting pretty worn out. A local shop told me, without inspecting it, that it probably needed all new components. I use it for fitness cycling and I like it pretty well, but it looks like it would be more expensive to replace the components than it would be to buy a brand new bike of the same quality. I'm going to train over the winter and spring to do a weeklong tour of Oklahoma next summer. I'll probably spring for a road/touring bike prior to that anyway. Is my old Schwinn toast, or can it be refreshed reasonably?
Thanks for the kind words about my site, Joe. Glad to hear it's helped you out. It's tough for me to answer your question because age isn't enough to evaluate a bike by. It's mileage, and how a bike has been cared for that tells the tale of what condition it's in and whether or not a new bike is needed. In most cases a bike that age will still be going strong because most people simply don't ride that much. But, if you rode it 5 days a week all-year long and put in say 10 miles a day, it would certainly be getting pretty worn unless you kept after it by replacing the chain, cassette cogs and chainrings as needed, tires, and other small parts, such as brake shoes and cables, etc.
A visual test will tell an experienced person a lot. If the bike is really gunked with grease and the tires are cracked and the cable housings are cracked, too and the cables rusty, that's an indication that the bike is in need of a pretty extensive service and may not be worth spending the money, depending on how you feel about the bike. Another good test would be to put a ruler on the side of the chain and see if you can measure 12 inches between 2 pins. If you get over 12 1/8 inches when you do this it's a sign that the chain is worn out and that usually means the cogs and chainrings might be, too, which means a fairly expensive drivetrain repair to get the bike running and shifting nicely again.
The best way to decide would be to bring it to a good mechanic for a look-see. They don't charge for estimates so that would be a good way to get an educated opinion based on an actual check of the bike rather than just an opinion out of thin air, which is what the first shop told you, it sounds like.
One thing to consider is that bikes have improved in those 14 years. Most significantly the shifting and braking has improved so it's easier than ever. Whether or not you appreciate the changes, and want to spend money to get them on a new bike only you can decide. That's easy and fun to do. You can just visit a bicycle shop and test ride some new bikes to feel how they compare. My experience has been that most people who do this realize that they get a lot more for their money in a new bicycle than what they'd get by spending money to repair the bike they already have -- not everyone, but most. Plus, for a major trip like a tour across Oklahoma, I would think you'd really enjoy being on a nice new bicycle that rides just the way you want.
Hope these tips help and have fun checking out new bikes,