I have no specific set amount of time. And I'm not sure if the OP means just practicing at home or with other musicians.
I'm not currently playing with anyone at the moment. But when I was... Our practice times were usually Tuesdays & Thursday nights, plus all day Sunday.
Alone practice time...
There have been times when I'll sit down for an hour or so. I usually set some sort of goal, like come up with a new, interesting melody or something like that.
Sometimes, I just noodle around with an unplugged one while watching TV. Sometimes, I'll hear an interesting melody & try playing it. A few times, I've put the TV on mute & tried to play whatever came to my mind, according to the program's scene.
Then there were days when I just bought a new bass. The day I bought my Warwick Thumb BO 6, I completely lost track of time & it was already 1:00am before I realized I should be in bed. Same thing when I got my Conklin GTBD-7.
I like to equally rotate my basses for pracice. Switch the bass each day. In addition to the 2 memtioned in the prior paragraph, I can also stay true to my Ibanez SR885 of 19 years, the travel-size Bassfish by Goldfish Guitars given to me by my wife this past Christmas time... Even equal practice time with the Ashbory. If/when I get a more, they will also fall into equal rotation.