It's better to apply NOW for a spousal open work permit. If you are not from a visa-exempt country and your spouse does not have an extensive travel history, it may be difficult to demonstrate that they would leave Canada at the end of your studies/expiration of their work permit. Furthermore, if you have less than 6 months left before your study permit expires/the end of your studies, you may not be able to successfully apply for your spouse's work permit. The earlier the better. In general, if you are not from a visa exempt country, it's always better to apply for a spousal open work permit instead of a visitor's visas. Your spouse can get the work permit now and then travel later when they're ready. Whatever you used to prove you would return in the first place, should be good for your spouse's application too. In general, property, family ties and good economic prospects could point to an applicant's readiness to leave Canada at the end of their legal stay. Good luck!
