Mirror wills. Does it give you security after death?

[purpledalmation]

DH and I have mirror wills with the survivor remaining in the property until death and each owning 50% of the property. House is paid off. The property/estate then would pass to DC. Very simple.
I thought a mirror will would give security that the will would remain in force and not be changed. However I'm now concerned that (if I died) DH could remarry and my 50% of the house could be disregarded, or my wishes. If he did not remarry, could he change his will and exclude the DC (he wouldn't but theoretically)?

@Lovelyveg82 he might have no choice. If he remarries but they subsequently divorce the new wife may get a share of your property. Or if he doesn't think to make a new will. Lots of situations that don't require your partner to be an unpleasant person.