Cheap mats are pointless in my opinion/experience as like Ethan has found they age badly. Yes you can clean them up to bring the depressed areas back up a bit but it's inevitably going to continue to happen. They are cheap for a reason. Buy once, buy OEM or at least the same material as OEM. Yes you may have to fork out 3-4 times the amount but it's worth it for an item that gets alot of abuse and will let your tidy interior down if looking tired.
Get yourself some decent mats, protect them with a Fabric protector such as Gtechniq I1, Gyeon Fabric Coat or Chemical Guys Fabric Guard