The length of the "ramping up period" for your ad campaing will require before you begin to see results is determined in particular by
The product purchase cycle:
How often does the consumer shop for the product in question.
Due to the fact that we eat more often than we redecorate, ads for food yield results much faster than ads for new carpet or furnishings. If people buy your product once a week, don't expect your ads to return a profit during the first week. If people buy your product once a month, don't expect to break even on your advertising during the first 30 days.
Solution: Commit to an ad campaign commensurate with your product selling cycle.
The longer your product purchase cycle, the more important it is that you plant your message before the customer, before the customer is actively in the market for your product.
The single-minded counter-argument of an overly anxious advertiser is, "But someone out there is ready to buy my product today. I want to reach that person and get his or her money today. I'll worry about tomorrows customer tomorrow."
The advertiser is like the hare in that timeless fable in which the patient relentless tortoise wins the day. The cheerful tortoise doesn't expect to win the race in a day, a week, a month or even a year. His goal is simply "to become the name customers think of immediately and feel the best about when they finally need what I sell."
The longer you stay with your plan, the greater your likelihood of winning the race.