Help Memory is silting up


My Wildfire S had gradually Alzheimered to low memory, so I was grateful when the update to Android 2.3.5 gave me a whopping 60 MB free phone memory. However, gradually it is silting up again and at present it stands at 47 MB. Since this update I have not installed any extra apps (apart from the two or three I had to remove first to free up sufficient space for updating). All apps that can be moved to the SD card, have been moved there and I religiously clean up caches with History Eraser. My wife bought her Wildfire S at the same time and has largely the same apps, but the memory of her phone seems to be stable around 60 MB. What am I doing wrong?

And further: if this memory creep is normal in Android, no amount of phone memory will ever be enough, or?