The timing of your leaflet drop can have a huge impact on your response rates. For example, you might not choose to sell shorts as winter is approaching. But if you were to sell them as Summer is approaching then your response rates will increase dramatically.
As this is your business, you will usually have an insight into when are busy periods for your products or services and when are quiet periods. You could choose to do a leaflet drop to advertise ready for quiet periods that you are expecting. This will help you generate an income during a time that is usually not too great. However, if your quiet periods are due to your products or services not being relevant to the consumer at that time, then maybe this is just something that your business will have to accept. It will be important to generate more income and customers during your busier periods to make up for these quiet times, so that is when you should conduct a marketing campaign.
As previously mentioned about shorts, businesses that may deal only in these will not have many sales during the colder months but should make enough income during the warmer months to cover the entire year. A lot of businesses are seasonal in this way.
Aiming for periods that you know the consumers will purchase your products or services will be one step in planning. You already know there is a demand during that timescale, and this should be advised to the distribution company who will take this into consideration when setting a deadline for the delivery teams.
Researching other companies and their time periods may help you with the timescale you choose. There are online forums where you could ask the question and see what worked for other companies and what did not. If you were to ask the distribution team you choose to use, they may have an insight into what worked for previous clients at what times also.
If you have a deadline date on your flyer for a deal or offer, then you must ensure all the leaflets are delivered with enough time left to make a purchase. This should be stressed to the distribution team, and they should stick to the agreed timescale as best they can.