J.S.
B.,
My sons are 20 months apart. I have 2 cribs. My older son is nearly 3, and is just now moving into a twin bed. He loves his crib, I didn't want to deal with moving him out since he had just started sleeping really well at about 15 months. I needed my rest, and he still was fine in his crib, so we let well enough be.
I bought a used one at the Roseville ECFE Stuff sale (a huge kids only garage sale in April every year) and actually bought a third crib to take to my mom's at the same time! They were priced so great (less than $30) it seemed silly not to just buy a second crib.
Good luck to you!
J.