To suck in the ppl on a daily basis, i would suggest to have something like a "2x xp for the first win"
Ofc i talk about wins vs real humans.
(if u also like to add one for cpu wins, im also fine with)So people got a reason to login in at all - at last once a day - and than may stay there.
[and now plz dont hate me] in World of Tanks < this really works well.
ppl get online to at last "double their tanks".... and often get stuck on that point couse they "miss a few more xp... just a few!"
So why shouldnt it work here ?
It rewards ppl for being loyal without breaking up something like the matchmaking etc.
And may i push it a little far here- but may it gives "non prem players" a hint how it would be like to have a prem account....
and encourage them to get one.
If ur allready prem guy- a 50% addition should be fine i guess- so its not to overrated. (something like that)
Its up to the admins how they like to balance it out.
And just get 2nd thoughts out of the way- i allready use prem ;P