So I'm mostly f2p player. (i have 2 tier 8 prems but other than that no gold ammo, prem account or improvements)
I have 5 or 6 tier X's and tbh i don't play with them.
For instance, I bought the tier X French light tank (the OG, not the wheeled abomination) which i dont even remember its name, and although i loved all of its predecessors I'm not interested in playing it (i have 3 battles with it). For 2 reasons. 1, i don't have any progress. Unless you have every tier X or unlimited time, it's "better" to play your lower tier tanks so you can research the next one. Playing with X gives you nothing.
Reason number 2, (most important to me) is the Credits. Not only you don't make cradits playing tier X, but most of the time you lose a considerable amount. High repairs, and the need to fire gold rounds to be able to pen some tanks makes it impossible to have profit. (most of the time) it's not sustainable. I have to play with my tier 8 prems to make up the loss, which loses me more time.
So, what motivates you to play with your tier X's?
(except unique tanks like shitbarn or TVP 50/51)