Max is a fairly tough chewer an in the nearly 7 years we've had him he is only on his 2nd nylabone so they appear to be fairly long lasting.

Same with Layton - he can kill most things within seconds (miliseconds if they squeak) but his nylabones seem to be lasting.

He goes through phases on them - will ignore them for weeks and then suddenly rakes them all out of the toy basket, splats himself all over the carpet (exactly wherever you want to be) and chew-chew-chews - only looking up with a blissed out "aaaah that's good" look on his face!