In VALID's Tree Risk-Benefit Management Strategy templates, apart from emergency work there are NO timescales for risk reduction work.
1) By setting work completion dates like 7 days, 10 working days, 4 weeks, 13 weeks, 3 months, or 6 Months (these are from real examples), you're quantifying the likelihood of failure part of the risk assessment with a mind-blowing accuracy that's simply not credible.
2) By giving a very specific period within which risk reduction work should be carried out, this is what you're effectively saying. The risk is not Acceptable or Tolerable. But, the risk is Acceptable or Tolerable for those periods of time. Then, suddenly, the risk is immediately no longer Acceptable or Tolerable after the last day.
3) If the risk is realised before the work completion date, then self-evidently your timeframe when the risk is temporarily Acceptable or Tolerable was wrong.
4) If your client can't get the work done within these dates, and the risk is realised, then they're hung out to dry.
5) You're unlikely to know what competing demands there are on your client's budget.