What to do with "older" lenses?

Hello, after not being very active for over a decade, i'm back in the "game". I realize there are new lenses, but also that due to the lower demand for DA lenses, some of them have gone down in price substantially (the 16-50mm f2.8?!). With that it means my lenses have taken a massive hit, to the point that they have virtually no value, i remember looking for a Tamron 17-50 f2.8 awhile ago going to a shop in London asking if they had a second hand one, and the salesman laughed at me and said "why would anyone want to sell this lens? it's too good, move on kid" - it took me half a year to afford one, which i did and still have, now they are for sale for 60 quid (!!).

So my question is: what should we do with those older lenses? keep them (for no reason) or sell them for almost nothing? or who wants them (photo schools?)??

The ones that would probably go:
- Tammy 17-50 (which has a bit of movement so no longer in pristine condition)
- Sigma 10-20 f4-5.6
- the older 50mm SMC A f1.7, great lens but i have a FA 1.7 and a K 55mm so hard to justify having 3.
- Sigma 24mm 2.8m macro (manual focus).. love it but not suitable for my shooting (kids moving, now overlapping with my new 21mm)

Any tips/advice welcome

I would say use them. Not all at once, but perhaps select one and then really get to use it over a period of time. Then move on to the next one, thus eventually giving them all a fair chance with the latest camera bodies.

It's a project I'm about to undertake for myself. The lenses are too good to just leave them on a shelf.

Yes sounds good in theory, I don’t shoot much though unfortunately and I have never been a fan of “forcing” myself to shoot (as in shooting for the sake of it). Maybe I need to start carrying my camera with me around

yes i guess it's part of this hobby, but it can be distracting to have too many options, in my case i dont know how to plan my next trip. On top of that i've bought two lenses + a camera in one month so my wife is wondering what is going on (though happy to see the results). Space is fake issue, but cluttering kind of is (i have a lot of music gear which isn't being used)

It also happened to me that i look for a lens and realized i've sold it many years ago. Kind of funny how one forgets, i've been digging old emails to realize i have owned many lenses.

but yes the default will be to stick to them, it's more a fear of things becoming obsolete (like my old MZ30), i guess it's different with older lenses like the K, SMC A, M etc.. where i don't mind sticking to them, but my view is more that i would prefer they get used than taking dusks and be found in my cellar 40 years from now when i pass away, i don't assume they can be recycled/reused to repair something else..

Those are good lenses so I'd say you should keep them and use them. I owned a Tamron 17-50/2.8 for a few years, bought new, and I only sold it when I managed to get a used Sigma 17-50/2.8 which I liked more. The Sigma didn't really take nicer pictures but it had a quiet built-in AF motor and was more solidly built, but the Tamron is a very nice lens and very capable.

You don't always need AF lenses to take pictures of your kids - you can take pictures of them in more reflective moments when they're still - watching TV, reading, playing.

I would add a vote for the Sigma 10-20. I had one for a long while and only sold it when I got a Sigma 8-16.
Both big and bulky but a god send when I couldn't use foot-zoom to get back to frame the picture I wanted.
Not lenses to carry all day every day but invaluable in circumstances when you know you are going to be crowded.

"Not lenses to carry all day every day but invaluable in circumstances when you know you are going to be crowded"

This is a good point. You wont miss some lenses until you need them.

I have built up selections of Takumar, K and SMC-M lenses between 24-300mm fixed focal lengths to use on full frame mirrorless bodies. They work very well and the medium focal lengths are also used for digitising 35mm negatives. For Pentax digital and film AF I have various zooms and fixed focal length lenses, mainly Pentax and Sigma. They work well and don't all get used all the time.

For what it's worth, I took my best photos of my children with an MX and 50/1.7 and 85/2 and an Olympus 35SP rangefinder. Fantastic to use, quiet, unobtrusive.

You speak of 'planning a trip' as if the experience will be dominated by which lenses you select. It is doomed to failure! The only lens you need is the A series 2.8/50mm macro and, if you are desperate, an F series 1,7X Auto Focus adapter to go with it. The only time you will need more is for highly specific purposes such as wide angle and high telephoto distances - and both of these will dominate what you do and where you go. The humble 50mm will range from centimeters to infinity - provided you have both it and a camera with you as well!