What is the convenient duration for potential client follow-up after sending the quotation?

Answering this question depends on way too many factors. I will instead state some these these:

1. What did the client indicate as a confirmation/reply date (if any)? What period did you propose for a follow-up/answer?
2. First-time client, second-time, a recurring one, a loyal one? Big name or...?
3. Is it B2B or B2C? Low or high competition market?
4. What is the product/service? Does it have an “expiry date”? Is it ready or needs to be made? Are you dependant on vendors to deliver?
5. What is the amount at stake?
6. What does your "experienced intuition" tell you?

It only depends on the decision and purchasing period,as for the frequency of following up depends on your communication skills so what is mostly important is not to frustrate or bother a client.