if u buy the 50 slots instead of 25slots is it perm 50 or does it only last 30days also and reverts back to 25 after 30days?

After 30 days you will have 0 slots if you dont pay again before the vault runs out. You simply need to pay all slots at all times (at certain numbers of slots you will get the price at some percent reduced)

The 50 slots however can ONLY be reduced again by letting the vault run out completely and then just buy 25 slots again. Increasing is no problem at any time though.

so if i want to exstend the next 30days with a 50 id have to pay 100 instead of 50 with 25?

exactly

Also if your vault expires with more than 25 items you will have to pay the amount for 50 slots to reopen it. ( even if it is 26 items! )

well thats good to know lol i was kinda tempted to open and just reopen for 25 and see if i could just pull out lil over time ect