I had the same problem, but i found out how to solve it!
Thunderbird version 22.214.171.124
Enigmail version 0.95.0
The problem was in my Password and Encryption settings, where the PGP passphrases was set to 'never remember passphrases' which i changed to 'remember passphrases for 20mins'. It seems to have overridden the setting specified in enigmail/thunderbird.
this is where the setting can be found here:
system>preferences>encryption and keyrings> the 'PGP passphrases' tab
I hope this solves your problem as well comrade!