The convergence speed of translation is not fast enough

[jpfeifer]

Have a look at the various threads related to the problem. E.g.

Longlasting IRFs

That is hard to tell. Most of the times, we actually want out model to feature persistence, i.e. endogenous propagation. In a quarterly model, 50 periods is a bit more then 10 years. That can still be considered a business cycle frequency.