Please refer to SQL Reference, Volume 1, Appendix A. SQL and XML limits.
There are new (much larger) limits defined for a LARGE DMS tablespce in 9.5 (don't recall if this applies to 9.1 also), but there is no mention of any limit for SMS tablespaces, probably because an SMS tablespace consists of multiple files (for each table and index). However, you may be limited by your OS in terms of size of individual files (for 32-bit systems), or number of files.
So you may be OK if you want to exceed 64GB, but I am not 100% certain about this.