Regardless of if it’s kicking or punching or both, you should have a plan going in. Just throwing anything and everything as hard as you can for as long as you can isn’t very smart nor efficient. That’s not to say a “burn out” round or two isn’t good, but you know what I mean.
Jobo made a great point - listen to your body. Keep proper technique. Also as he he said, define what you’re looking to gain and work towards that.
When I focus on kicking, I do a bunch of things. I never counted a total though...
Fighting stance, and I’m pretty much taking a small step/shuffle on every kick.
All kicks done with front leg x 20, then rear leg x 20...
Front kick
Roundhouse
Side kick
Hook kick
Inside-out crescent kick
Outside-in crescent kick
After that, I’ll switch to opposite foot forward and repeat. I sometimes throw in an additional kick, replace a kick, or add/replace a kick with a combo like front kick then on the same leg roundhouse without touching down. Depends on my mood.
When I’m doing that many kicks, it’ll be a balance of speed and power, but mechanics come first. Sometimes I’ll do 10 of each kick instead, but I’ll focus far more on speed or power. Depends on my mood.
Regardless of how many and what I’m doing, I keep a good pace. I try to get my heart rate up and keep it up. Not all out heart rate, but pushing myself pretty good.
After all the kicks, I’ll do some kick-punch combos. Something like front kick-straight left-right hook. Sometimes I’ll go slow and pay attention to where my feet are landing, where my hands are, my angle of entry and exit, etc. Sometimes I’ll just go fast. Sometimes I’ll go hard.
On punching focus days, I’ll do something similar, only moving in jab x 20, jab-cross x 20, jab-cross-hook x 20, etc. Just like kicks, some days I’ll go slow and pay attention to my movement and mechanics, so days I’ll go at a cardio pace, some days I’ll go all out power.
Then other days, I’ll simply do rounds. 12 x 2 minutes, 1 minute rest between rounds. I’ll constantly do combos, moving in and out. I’ll have a fight in my head
The biggest things are change it up, alternate heavy/difficult days with lighter/more technical days, and get adequate rest. Stretching before and after too. And I really like the foam roller for my upper back after I’m done. The hot tub was great when I had access to one afterwards to recover.
To take it up another level, I wear a Fitbit and track my heart rate. I’ll work harder when need be, and back off a little when appropriate.
Sorry for the long manual here. I did this about 4 x a week when I was getting ready for a tournament. It helped A LOT. While it seems like all that would take forever, from warmup to cool down it would take about 50 minutes total.