Will Mavis and Jonathan last forever?🤔

As I watched the movies I did the math between the Mavis and Johnny. Mavis was 118 and Johnny, 21. In the second movie they start off probaby countinuing from 118 and 21. They're married and a year later they have Denis, so they're 119 and 22(a possibility). By the time Denis is 5 Mavis is around 124 and Johnny about 27. So if Johnny keeps aging(he will apear older) and Mavis will slowy age(considering Dracula's appearance)which would make Johnny closer to dying (which is something nobody wants to happen). My question is how is Mavis going to keep Johnny with her? Will she bite him? Or, Will she let him die?...