If you have had your divan bed and mattress for a number of years and are looking into replacing only the mattress, you may want to consider replacing the base as well. The base is prone to wear and tear just like the mattress, albeit to a lesser degree.
When making the choice between a divan bed and a bedstead, most people will opt for the divan bed, thinking that it will be far more comfortable. While this is true in many cases, what if you simply must have a bedstead? It is important to bear in mind that a bedstead is not actually a bed in itself, but rather a piece of furniture that you put a mattress on in order to make the bed. The mattress then takes on a primary consideration in your purchase. There is simply not much sense in spending several hundred dollars on a bedstead, then skimping on the mattress thinking that you can merely replace it after a few months.
If you are in the market for a bedstead, make sure that you inspect the base thoroughly for solidity and robust construction. If it does not feel hefty or solid when brand new, think about how it will be like several years later on. You should definitely resist the temptation to buy a cheap bedstead, as it is a decision that you may end up regretting when you find that it does not stay in satisfactory condition for very long.