I'm guessing that it's different for everyone but...
When I first started I could taste some flavors and not others. Within about a week, I couldn't really taste anything other than menthol. Throat hit went down dramatically with the apparent loss of flavor as well. It was driving me 'nuts' reading people's reviews of ejuice...'oh, the flavor,' 'tastes yummy,' blah blah, but I kind of had a sense of what they were talking about based upon my 'early' days.
Desperate, I went to a Silver Bullet at 6v and now the only thing that tastes decent to me and knocks my nic fits down is 48mg menthol

. This set-up also got me off of constant pacifier mode and now I can take a hit or two every once in a while and then put the thing down.
In my scramble to get a Silver Bullet I also ordered a load of flavors from diyflavorshack. I received those shortly after the SB but can't use them, they taste like pure, hot steamy sugar coming out of the SB, quite sickening after a couple of hits (like I say, I'm sure it's different for everyone, no knock on the 'flavorshack' at all, just doesn't work for me or my set-up).
I am about to try to begin mixing my own. Ordered 60mg nic juice, pg, vg, flavors, even a 'chemistry set' (sort of) so I'll see how that goes but in the meanwhile I'm quite happy with the menthol and have about a week's supply of that left (note to self: order more 'staple' 48mg menthol juice before it's too late).
If anyone figures this diminishing flavor thing out, please, do-tell (report back).

as it'd be great to know.