Bottom line---if you trust in the quality of the company you purchase from, you will have no problems.
I don't understand what that means. If I trust Merlin, that doesn't mean I won't have a problem with my bow in 5 years.
Like I said, I realize it isn't an owner's lifetime that they're referring to, but I also don't believe they are all simply "blowing smoke". I know of numerous examples of great service (for free) on warranty isssues that occured many years down the road, from a few different companies.
From what I've seen, it seems to be the norm to offer the limited lifetime warranty. It is offered by Mathews, Hoyt, Parker, Archery Research, Bow Tech, PSE, Kodiak, Diamond, High Country, Champion, McPherson, and Proline, to name a few.
To me, it isn't a question of how long they keep the parts. Merlin may not keep theirs any longer. They question becomes, when they can repair it, who pays for it?