How long can I carry over my RRSP contributions without claiming them?

I'm in Ontario, Canada. I've been on sick leave for about 5 years, which means that I have no taxable income, but I've still been putting money into my RRSPs. I'm planning to claim the deductions when I start earning taxable income again, but I wondered if there's a limit to how long I can carry the contributions over without claiming them.