While what PMM said is true, the 4 year max does not apply to SOWP as long as the principal applicant has a valid work permit.
It also does not apply in other cases e.g. for a NOC 0 or A jobs on work permit in case of nominations etc.
For instance, I had a 3 year LMIA based work permit and my spouse got a SOWP based upon that. Now I got another job + similar work permit (no max because I am NOC A). So my spouse again received another 3 year wp - similar to the expiry of my current one.
Details are here under exceptions tab
http://www.cic.gc.ca/english/work/apply-who-eligible/four-year-maximum.asp?s=1
Coming back to your original case you need
a) to prove common law - which means you must have been living together for at least a year
b) Spouse of a PGWP holder is ONLY eligible for SOWP if the principal applicant also has a skilled job offer i.e. NOC 0, A or B. You could apply together provided your spouse has a skilled job offer to submit along. Else you do not meet the requirements.