How many threads your system can cope with is kernel dependant. Luckily, there are ways of testing that, which (oh what surprise) you can find by searching via google. For example, I just searched for
linux maximum threads and it came up with
this page which has a testing program written in C and (quite possibly out of date) instructions on how to increase that number. If you want to do so, I'd just search on google (or any other search engine of your choice) and try to find something. It's normally a quick and effective method.
Greetings,
Nepomuk