Age discrimination is a very tough issue because there ARE trends that surround people at various age groups. I've hired people of all ages and experience levels and in my experience it's MUCH easier to get a young person up to speed than an older person, provided they have about the same level of experience. It's also MUCH easier to get extra time out of younger people than older people. Whenever crunch time happens it was like pulling teeth getting our older developers to put in extra hours - there's always something - a daughter is graduating, a health issue of some sort, etc. I'm not saying these aren't valid reasons, I'm just saying these things always seem to crop up at the wrong time. Also, younger people (especially if they are really into programming) are way more willing to keep improving and learning on their own time.

I'm 34 now and I can already feel it. When I was young I would spend hours upon hours writing code and would suck in as much knowledge as I possibly could, but as I get older and start having more life issues I'm finding it harder to motivate myself like I did was I was younger. It's much harder to do these things when you have a family that demands your attention. I haven't 'lost it' yet, but I can feel it and by the time I'm 50 I'm sure I'll be a lot like those older developers I mentioned above (which is why I plan on getting out of this industry before then).

Software is a tough industry because you need to keep improving and keep learning new technologies, frameworks, APIs, etc. It requires a lot of dedication and a willingness to put in a lot of time outside of work to keep yourself relevant.