Sir,
I use try and error method to improve imputations with a database of firm's variables (time series cross section data with collinearity:1800 rows-observations, 163 firms, 43 column-variables,) .
It has been helpful to limit number of draws to 100 (,emburn=c(20,100)) after getting convergence with 400 and 500 draws and seen disperse grafics (a.out, dims=1,m=5) visually converge at draws 70-80.
Also taking out variables for collinearity, adding lags and leads and using polynomials (polytime =3, much better than polytime =2 or not polytime at all).