The Lost Lowdown

It was not Penelope or their love that really was Desmond's constant. The thing that did not change was her phone number
7946 0893.

A static number is a constant.

Perhaps our favorite numbers
4 8 15 16 23 42 (108)

Are constants that keep time from shifting. As soon as Desmond stop putting these numbers in he phased out of time.

Since they (Lost Writers) said that Ms Hawkings is the be-all end-all of the Paradox/Time Travel/What-Is-Going-On-With-Desmond storyline, and since she clearly states that Desmond and Penny will NOT ever marry or be together - that the Universe will course correct this - then maybe you are right. Though they do have us believing that Desmond and Penny are destined to be together...ugh, too much "it's this...but it could be that..." crap...