If you're going to use a long password there is no point to using the TPM as the length of the password itself is enough brute force resistance.
In my opinion all the TPM achieves in this case is ensuring you lose your data if the machine dies (or if some OS update fucks up and doesn't properly ensure the TPM acknowledges the new version as valid).
That said it does help against the so called evil maid attacks, given that it would lock itself out if anyone modifies the OS, so if that's part of your threat model then it is useful, I guess.