Multibit creates new wallets

[arfo]

Multibit keps adding new wallets about everytime I use it. File names of the wallets are the oroginal wallet name with a timestamp added. E.g.
MyWallet.wallet
MyWallet-20130422052833.wallet
MyWallet-20130422052833-20130426075515.wallet
MyWallet-20130422052833-20130426075515-20130426080647.wallet
MyWallet-20130422052833-20130426080647.wallet
MyWallet-20130422052833-20130426080647-20130516110128.wallet
MyWallet-20130422052833-20130426080647-20130516110128-20130521084212.wallet
MyWallet-20130426080647.wallet
etc..

Is this the expected behavior?
If so: why? Which wallet file should I open?
If not: what can I do about it?

br
Arne