Expiry Date.

I was wondering if relationships too came with an Expiry Date. If the answer is 'No', well, then that's the end of discussion. But if the answer is 'Yes', then we do have these two possibilities here :

1. Are they like the Expiry Dates on those medicine bottles, where even if its past the date you can still use the medicine, but the result might not be really soothing.
2. Or are they like those softwares which you can download from the net for free, those '30-day free trials'. Once the 30 day period is over, you will not be able to use the stuff.

I am not really of any help here for anyone, isn't it?