One of my first instructions for owner practice when just starting training is to keep it short and sweet, a few times a day, with ample rest periods between practice sessions. After a few weeks though, I start encouraging the clients to stretch the practice out, mix up the commands, and most importantly, make it fun for your dog.
That's the part I want to talk about, how do you make practicing commands fun? If the timing of your rewards/praise is on point it should already be pretty fun. But, we can always do some things to make training time indistinguishable from play time.
Use your time playing fetch to practice recall, retrieval, and drop commands. Use tug to practice out and leave it commands. The point is to use the distraction of wanting to play to bolster the strength of your dog's obedience.
A couple of years ago I created a new command for my boxer, Otis. The command is called "clean up" and consists of him collecting his toys one by one and bringing them back to drop them in his toy box. This one little game encompassed several skills at once and gave Otis tons of fun to practice.
Make up some training games of your own and watch how much fun your dog can have while working.