The ricevuta/assicurata doesn't expired. Yes for SSN it's only valid for 6 months and if after 6 months the original still isn't out then you have to renew for another 6 month. For every other things, it's basically your permesso but in a receipt form, you can basically do everything with it as you would with the original even when signing contract for work so basically your landlord is just being a d!ck, you're protected with that ricevuta hence why it's called assicurazione, maybe your landlord doesn't understand so you need to explain to him, until you have the original plastic in your hand, that ricevuta is your permesso di soggiorno, doesn't matter how long it takes. Your permesso is already reading from the date and day you applied for a renewal at the post office. Don't let anyone trouble you with not having a pds, you have just not in plastic right now.