Realistically a collection of white belts aren't going to challenge you much if you've been training for 14 years.
I'm reasonably new, tiny and a girl so I'm probably not ever going to find myself in a situation like yours, but some of the ways that my guys train with me might be useful ways that you can challenge yourself instead.
Teach me! Teach me!
Several of the more experienced guys I get to roll with turn each roll into a coaching session along the way. If I make a mistake they choke me silly, then point out the mistake and help me correct it. If there's a technique I don't understand or don't recognize they'll explain it for me. Obviously this is a huge boon for me but for them it's helpful too, because in order to explain something to someone with less experience you need to really understand it yourself. This isn't going to directly help your technique, but it might help you understand your techniques and concepts better. You have time to really think about why this stuff works. It's worth something.
Wait, how did I get to mount?
I'm a hundred pound teenage girl. I don't get to play top game very often against adult guys. Except the clever ones who realize that a training partner who isn't in your league is an extremely useful person to practice defense and escapes against.
Give your white belts opportunities to attack you. Start under mount or side control. Deliberately give up your back and let them start working for that choke. This gives you heaps of chances to practice escapes and defensive techniques, because they probably won't finish you immediately like someone of your own skill level would. More time in bad positions improves your game for sure, even if you have to deliberately engineer those bad positions yourself.
Play your 'C' game
Training partners who can't really challenge you are the best people to polish those techniques which aren't your best 'high percentage' or 'go to' moves against a challenging opponent. I'm forever getting people try new things on me, which can be hilarious and really isn't bad for either of us.
Make a game of it
There's a couple of purple belt guys in my gym who usually get assigned a 'challenge' for rolls with me. I might not be able to give them much of a contest under normal circumstances, but it's a heck of a lot harder for them to finish me if they're only allowed to submit me with a specific technique and I know what's coming. They still do, but that's okay!
So be creative and challenge yourself. One roll you're only allowed an armbar on the guy's left arm. The next roll you have to 'call' a submission before you try for it. Whatever. Make your own difficulty.
Smash me! Smash me!
Some people will have tantrums if you destroy them, others will be fine with it so long as you're nice about it and don't do it all the time. I was the happiest camper in the world the first time one of our smaller guys said "I'm competing this weekend, do you mind if I turn up the intensity this roll, I really want to work on getting my submissions nice and crisp". Maybe I'm just crazy, but it was pretty fun to get tapped fifteen times in ten minutes.
So pick the right people and occasionally you should be able to really bring out your 'A game' for at least part of a roll.
Find somewhere you don't have to do any of that stuff...
Realistically you're probably going to want to find somewhere that has training partners who can challenge you, even if that means travelling a bit further sometimes.
If that's not an option, hopefully some of those other things might help keep you somewhat sharp anyway. Good luck! :)