I agree with most of what Homer is saying, but not all. Anyone getting into any technical field today had better realize that if they want to stay in a technical capacity they will have to constantly be updating their job skills. This can include college coursework and possibly an advanced degree, or accumulating certifications and working open source, etc... The alternative to this is as Homer describes....become an expert in a product or field and hope to hell the maintenance will keep you employed.
A lot of senior technical people get comfy in their lifestyle and expect their experience is enough to carry them till retirement. I know I was fed that line in college. "Once you get your BSCS, you'll be set for life".
I believed it until I experienced a few rounds of downsizing, it's amazing how sobering it is to watch a good % of your co-workers get the boot.
I'm old enough to have used a slide rule in college, I'm in the finishing up stages for studying for the SCJP. Over the past few years I've taken college classes in OOAD, Web Design, and even Geographic Info Systems (Grad course). After writing C and using Oracle SQL for the past 10+ years
I now write JSPs, servlets,etc...So it's not all doom and gloom,but I have spent alot of time (often between 4-7AM)studying.
Of course the alternative is going into management, but thats a topic for another post.
Anyhow, I think age is a factor, but remember an employer is looking for the best candidate for them. If you can show your not living on past accomplishments and can bring something to the table being over 35 shouldn't be a problem...
Hope this helps.