Welcome (first post) to FT!
To prevent your points from expiring without signing up for the jetBlue AmEx, you might want to consider buying points to top off your account. Depending how many you need, it may very well be a viable option. Myself personally, I would say any account with OVER 50 points and some about to expire it may be worth doing this. It's $5 per point with a small transaction fee and 7.5% tax I believe. You can do so via the link on your TB home page. Also, here's some info from the FAQ section:
http://help.jetblue.com/SRVS/CGI-BIN...ase=obj(387161)