He long is the waiting period to have a re-appraisal?
If you're asking how long a successful appraisal is "good for" the answer is three years. If you've had an unsuccessful appraisal then the answer is less clear. The SEI does not provide any formal guidelines for this, as every organization is different.
It really comes down to the depth of the weaknesses identified during your appraisal, and whether or not you can credibly make the corrections, build up some maturity, and show results on a reasonable amount of projects.
In some companies this could be six months - in others it could be six years. It just depends on your situation.
The bottom line is that there is no formal requirement from the SEI on this but you will need to ensure that your Lead Appraiser is comfortable with your progress from the last appraisal before you conduct a second one.