Rerolling is always a tough process. I also don’t know how the Achievement points display works anymore… it shows 6k for this char, but 17k when I log in game. So if you care about that sort of stuff… idk, might be something to consider.
Personally, I played a warlock in Vanilla and TBC, but I always wanted a DK so I instantly rerolled to one in WoTLK and made it my main.
The warlock was where I had the original netherdrakes, nether rays, the Tabard of the Protector, and all the cool Vanilla items. But those things will always be on that char’s bank/inventory/storage.
DK lasted as a main from WoTLK to WoD when it was no longer fun to me, went Mage for a bit and then Paladin. So I had to let go of even more reps and fun items bringing up memories.
I wish a lot more stuff would be account wide… but especially reputations and their progress bars.
That one hurts the most, as I had to re-grind all the Legion reps on this character right here because the Mage had become unplayable to me compared to the chad melee lifestyle.
To answer your P.S. question, I think the timing doesn’t matter that much. Your conviction does.