A question was posed as to re sticking the mats would void the warranty on your cricut machine. After reading the warranty on the web site the only thing I found was this on the first page line item two
This Warranty does not cover
2.Cutting mats, whether supplied with the Machine or sold separately from the Machine.
it further states in item four the Warranty does not cover
4.Failure by a products for which PROVO craft is not responsible.
So in my opinion re sticking the mat does not void the warranty as long as you don't spray the adhesive over the whole mat and cause the rollers to become sticky. There is not a life time warranty on this machine it is only a 1 year warranty on the electronic parts, motor and wiring, switches, speed control, LCD screen and a 90 warranty on all other non electronic parts. This is from the original day of purchase not when you started using it.
If you would like to read the warranty on the cricut machine here is the link. so you can come to your own conclusion
http://www.cricut.com/res/mwarranty/CricutMachineWarranty.pdf