It's difficult to establish when you should practice SHO/WHO or how much you should practice SHO/WHO without first defining your goals.
If someone is spending half his range time on one handed skills, there needs to be a well thought out reason. That reason could be:
- it helps me with my other shooting
- I believe that people are often forced to shoot SHO/WHO in gunfights
- a game I play puts a lot of emphasis on SHO/WHO
... or whatever. But don't just shoot x-number of rounds or z-percentage of your practice SHO/WHO for the heck of it.
I'd say I put about 10% of my time into SHO/WHO. If I was practicing half as often as I do now, I'd probably up that number a bit. However, if I was practicing significantly less than I do now, I probably wouldn't put more time into SHO/WHO. When training resources are limited, the smart thing is to put your effort into high likelihood tasks. Getting good enough at SHO/WHO to be legitimately
competent under stress -- and if something forces you to shoot one handed, you're probably already a tad stressed -- takes substantial time and rounds.
It's not wrong to train for the worst case scenario, but it's a mistake to ignore skills you're actually likely to need in favor of the one in a hundred problem. People like to say, "Yeah, but what if you're that one?" to which I can only respond, "What if you're one of those ninety-nine instead?"