Dude, you have no idea what you talking about, I just picked on your line that phone will become slower with ''usage'' like by calling/texting and laughed, simple, duh, every1 knows installing more apps, especially 5000 songs on memory card, slows it down.You don't know me, so don't assume that I'm s60 newbie, I've been using Nokia phones since you can imagine, I've worked for Nokia too in Uk as technician in service center,100s of phones used to come everyday for repair, but I never bring in topics like CPU/RAM/ALU to confuse and worry others, We all got your point about CPU, but just leave it alone and move on.When you have the phone in your hands then you can complain about the CPU/RAM, seeing is believing, so far I've seen good performance by n97 and I know what apps to install and to answer your question,I never said that don't install anything.Whenever I buy a phone, first thing I do after full charge is install tons of apps.I've 10gigs of Nokia apps/themes/games.
Don't install unnecessary themes, especially the one which are animated and not properly compatible with the phone.
Don't install an app which triggers other processes in the background when the phone boots up.
Don't use a counterfeit memory card, it will get corrupted very often and phone will slow down/freeze unless you take the memory card out.
Don't leave only 40mb free out of 32gb built in.
When you done with music player, exist it, especially when you have 5000 songs.
Obviously, use taskman/handytask to manage processes.
Any more ways you wanna know how to get best performance?