In addition to, what has already been said, being unbalanced in only going to be a problem, if our opponents figure it out and make correct adjustments to exploit us. So its definitely something, we need to worry about, if we are Daniel Negreanu or Doug Polk, and is going to play 25.000
hands in an online heads-up match against the same opponent.
But if we are playing in soft live games or in micro or low stakes ring games online, the risk of getting exploited is much lower. Online we are often playing in large player pools, so its difficult for our opponents to figure out, what exactly we are doing. They often wont have enough data, even if they are using a HUD, and they might also not want to spend the time nessesary to deeply study our game.
But thats not to say, that balance is NEVER important. If we only ever 3-bet premium hands like JJ+ and AK, then this will show up on our opponents HUDs after a while, and they might start to not give our 3-bets action. Or at least the better opponents will. So the more common a situation is, and the more we play against the same people every day, the more we should try to stick to a fundamentally sound and balanced strategy.
Another example could be, if we C-bet a flop like 883 with air and get check-raised. Then we should at least consider, that maybe we are C-betting these kind of boards to wide, and maybe that got exploited by our opponent. So maybe next time we check back such a board against that particular opponent.