I can totally understand about the feet/legs/back thing. I'm no spring chicken, and my back isn't great. We usually don't spend very long on stand though. 15-18 minutes is normal. Sometimes a little longer. Sometimes we set up, call, kill a couple coyotes, and are out in less than 10.
I'll throw this in too since you say many of your sets are tight. Any time a piece of your anatomy is anchored to the ground then speed and flexibility suffer. One thing I really do like about standing is how fast and flexible I am with changing targets. While standing if you will put about 10 feet between you and your partner either of you can move really fast in about a 270 degree arc (don't swing across each other) to adapt to changing opportunities. And if you do need to shoot to the other side of your partner you just pick up the tripod, take 2-3 steps, plop it back down and you have a whole new field of fire.
Last thing. Up above you remember I said about setting the tripod/gun up lower than you think? Well stability is one reason to do that (even though it makes legs/back hurt more, so tradeoff). The other is up/down shooting angles. If you set your gun up too high then while it makes it pretty easy shooting uphill it makes it really tough shooting downhill. You have to get way up on your tippy toes (not very stable) to shoot. Set the gun up lower and you can depress the muzzle much more before you run out of leg length to get the buttstock up high. This is an issue for us not just calling but shooting sounders of pigs. Get your gun set up too high and if they run in close they can get under your gun where you can't shoot. Especially if they are close, and downhill. Standing gives lots more vertical options, lots faster. You can even set the gun up pretty hard on the low side and if you need to shoot hard uphill just drop to one knee behind the gun/tripod.
The best thing to do is go out and play with it during the day with a normal scope. Set up different ways, play with different options, see what works for you. Don't be scared to think outside the box.