The only heap space problem you can have is "not having enough space allocated for your app". Anything else is not a heap space problem.
You can make your app more lean (as far as memory goes) by not holding on to object references any longer than needed but, often, letting go of them too soon will make your app less efficient in other respects.
If, by caching objects/data in memory, you can avoid repeated disk i/o or database transactions you can greatly improve the performance of your app.
In other words, there is nothing wrong with an app that requires lots of memory, as long as it's putting it to good use and is running on a machine that has the ram that the app needs.