You have to keep your old ones as you get to the high tiers to keep making credits.
My current garage:
Tetrach - Premium
Matilda - Elite
M4A2E4 - Premium
PZIV - Elite
Cromwell - Elite
Comet
Churchill VII - Will probably keep (about 7000 xp away from Black Prince)
GW Panther
E-75 - Elite
T-54 - 20000xp needed for T-62
Object 704
Just sold an M4A3E8 might buy the T-20 when I have more credits. Have 2 spare garage slots.
My current garage:
Tetrach - Premium
Matilda - Elite
M4A2E4 - Premium
PZIV - Elite
Cromwell - Elite
Comet
Churchill VII - Will probably keep (about 7000 xp away from Black Prince)
GW Panther
E-75 - Elite
T-54 - 20000xp needed for T-62
Object 704
Just sold an M4A3E8 might buy the T-20 when I have more credits. Have 2 spare garage slots.