A good base can perform magic to your mattress. Combining a new mattress with an excellent bed base guarantees you maximum benefits of comfort and firmness out of your new mattress. Similarly, if you engage a low-quality bed base, you will not get the best out of your mattress. Note, the bed base is the foundation of your mattress. Nothing else keeps your mattress in position. Therefore, if the bed base sags, the mattress will do so as well. This is real even for a new top mattress.
Perhaps you have taken long since you made your last mattress or base purchase, mattress technology would have changed over the period. Consumers and dealers have discovered that a base and a mattress both have a common effect to each other. An excellent mattress is amazingly comfortable and lasts longer on a suitable base say that of an upholstered queen bed for instance. The same mattress on an inferior base denies you of the comfort and never lasts long.
The point here is, you can never reason about your mattress independently. Instead, you have to reflect on the bed as the main sleep system that contains both the base and the mattress. Does your sleep system make you comfortable? If your bed feels lumpy or sags, or if you wake in the morning and feel tired, then the problem is with the sleep system. The main issue may be just the base, the mattress, or a combination of the two.