[plt-scheme] typed scheme type checking takes very long

Hi all,

I am wondering if I'm doing something wrong using typed scheme - it takes about 20 seconds on my machine (Mac Book Pro with 2,4 Ghz Intel Core 2 Duo and 4 GB) to typecheck about 130 lines of code, consisting mainly of data definitions and functions (that is, after enhancing the memory to 256 MB "on demand")...
Is this normal, and if so, what could I do? Further enhance the memory (where can I do this?). Or might there be a problem in the code (I can send it)?

And an additional question (just for curiosity, for now) - when a typed scheme application goes "productive", would the type checking be disabled (for performance reasons, with no-check), so it would be mainly a help to the programmer during development?
(BTW although I'm at the beginning only, I already start to find it really helpful, and the error messages are informative, too :-) )

Many thanks for any help,
Sigrid