You'll get varied answers on this. But, single-handing especially, I think the best general statement is that if you're not racing, you can just leave it centered until you are settled in and ready to fine tune mainsail trim - like you're going be on that tack for at least a bit.
But, I think that the better answer is that it depends on what you want to get out of sailing. For some people, the whole point is to sail as efficiently as possible at all times. Since you asked the question, I expect that's not you. For others (like myself), it is about other things. I have learned to instinctively trim to "good enough" very quickly and most of the time don't care about another 10% efficiency. If I run out of things to do and think we could improve trim, I might start tweaking things like the traveler. Otherwise, I just leave it centered.
But, also, I sail in conditions that are changing all the time. So, getting too fussy with sail trim is kind of pointless. If sails are out of trim I have three choices, adjust sails, change heading, or wait 2 minutes - all have about an equal chance of resolving the situation.
So, for my sailing style, I have just three traveler positions: center, windward, and leeward. Not much point in anything more fine-tuned. And, I stay centered most of the time, even though I have crew that could adjust it. If I really need to pinch, I'll set it all the way to windward, if I plan to be on that tack more than a few minutes. If I am on a broad reach or better, I'll set it to leeward when/if I get around to it.
There are some people who will claim this is not just about efficiency but also about safety. I, myself, reject that, especially on your size of boat ... for most cases ... there are some exceptions.
