I think this scenario answers your question.

If you have 1M vests, and you power down, after a year youll have 500,000 vests, and 52 payments remaining of a little less than 10K vests each.

If you now cancel the power down, then restart it, you will get your 500,000 remaining vests in 104 payments of a little less than 5K vests each, over a period of 2 years. That is to say, you will have started fresh.