Does Change in Temperature affect beer?

I've always heard that it is not good to let beer get warm once it has been cold. But I've recently heard that that is just a myth. Or at least once it comes to beers that have been pastureized. If they have been pastureized the change in temperature wont affect it unless your change in temperature is drastic not the typical fridge temp to room temp. Anyone know if this is accurate? What about homebrews? Would temperature change affect the beer? I've placed a keg in the fridge to force carb it but eventually (cuz my fridge is small) I will need to take it out and make room for my next beer. Will taking the keg out and letting it get warm again affect my beer?

as long as it is done fermenting, and is not exposed to these temperature changes for a long time (more than a month or so in the keg) it should be fine. atleast as far as i know.