I have a Rockboxed Sansa Clip+. I like that I can set it to turn off automatically, so I can fall asleep listening and not have it play all night. I also like that it will pick up right where I left off the last time. That's nice for podcasts and books. I suppose that might be what you meant by bookmarking.
You can buy a one-foot 3.5 mm extension cord with a right angle plug for a few dollars to avoid repeatedly stressing the jack.
I had one for a week and returned it. IIRC there was no sleep/standby feature. You either lock it like an iphone screen or turn it off. But it starts pretty quickly when you turn it off, so that's not the problem. For me it was just too slow and instable. There is a github repo with all the issues (https://github.com/vext01/hiby-issues) - check that before you buy one.
Why are yours dying so fast? (Alternatively, why do mine hold up so well?)
I have had two Clip+ in the last 15 years. I retired the first one because I broke the clip off; it still works otherwise. I was using them about 2 hours a day until the pandemic.
I have had several clip+ses over the year, and the one thing that died every time was the onboard flash (which prevents the player from booting at all). I resurrected my last one where it was only corrupted and not dead, but I did not have other issues otherwise.
Now I am using an hiby R3, which is quite clunkier, but allows me to choose between microsd storage and streaming from the phone in high quality, while also having 2.5mm balanced IEMs (kind of a gimmick, but I like their sound a lot).
edit: and of course being able to finally ditch USB-mini is great.
For anyone affected by this, a simple trick to reviving a Sansa Clip+ that won't turn on is to hold the power and home button simultaneously for about 20-30 seconds. Let go and press the power button and it might turn on.
I'm not sure what causes these players to become unresponsive. It's happened to me when it tries to play an unusual file or after I've transferred music to the device and left it plugged into the computer for a while.
They are still my favorite standalone portable mp3 player, even with the stock firmware.
One ended up on a trip through the washing machine and didn't survive. Another's jack broke (common problem that I didn't back then know how to prevent), and I broke it even more when being an idiot in trying to fix it. The last wore out its internal flash (I think).
You can buy a one-foot 3.5 mm extension cord with a right angle plug for a few dollars to avoid repeatedly stressing the jack.