Depending on the location, how many other clients you have in the area, the house, the personality of the client, the amount of quality you think the customer will expect, etc, etc, you can give them a little different quote. Also take into account the size of the lawn, obstacles and areas that may take more time I.E areas that you can't fit the big mower in and have to push mow.
If a customer requests a bi-weekly mow, and it is a reasonable request (on a slow growing lawn) allow it, but charge a bit extra.
Last but not least, If you want price bargaining power, quote a little high on the price. Giving a higher price first allows room for bargaining on the customers end. If you first give you bottom line price then people’s tendencies will be to negotiate anyway and you will have no room to bargain with. Also, if you give the high price first and they don’t negotiate, you get more for the property anyway so it’s a win-win situation.