It's really your own decision to, but a lot of people tend to strongly advise against such train of thought; rather than becoming a jack of all trades, master of none, imagine if you put all of that time you put into all 10-20 of your 'mains' into just 1 or 2 favored characters? You'd likely be much more proficient at those two characters than you are with any one of your many current mains. The speeds and distances of every movement, the difference properties of every attack, the variations between every techs/mindgames/playstyles...at least for a good 99% of us, they're all far too specific to each character to be mastered to their utmost when maining anymore than a few characters at a time, and even if you do manage to, you'd have to constantly maintain that skill level by practicing each constantly. Even for professionals that main several characters, they often learned them one at a time, and still consider a given 1-3 of them to be much better than the rest. If you feel you can main them all just as efficiently as you could if you chose to prioritize one or two of them, or at least fewer, then go for it - that's a crazy amazing and you should keep at it. Just offering my two cents to consider, from what I've picked up reading the general community's opinion.