Don’t forget that this what these guys do for a living, both performance and teaching. Therefore, it is (or was) in their interests to put the time in. Don’t feel bad about not being able to have the same dedication, their drive often comes from a different place. Of course, I realise that there are those who can and do have this level of commitment without the financial driving factor, but I imagine the vast majority of us do what we can, when we can so that we can also pursue the other activities that make up our lives. In addition, there are potential physical limitations that might stand in the way of that high level of dedication to a practice regime. Having had a lot more time for practise recently, coupled with the added drive of a new bass, has resulted in me acquiring tendonitis in my left forearm (too many one finger per fret, across the things and up the neck exercises). If you don’t rely on playing for putting food on the table and paying the rent, do as much as gives you pleasure (surely that’s why one does it).
Regarding vibrato, I come from a guitar playing background where side to side vibrato seems to the de facto technique. However, when I came to play fretless bass (I don’t remember using vibrato on fretted when I first started and turned to fretless really quickly), I naturally used and use the nut to bridge action and I don’t know why (perhaps I was tying to emulate Pino). It’s certainly more controllable than sideways movement and, therefore, more subtle and pleasing to the ear IMO.