Abhirup,
If I see this right, then the "official" name of the technique you are using is called The Method of Loci. It is a is a mnemonic device adopted in ancient Roman and Greek rhetorical treatises. In basic terms, it is a method of memory enhancement which uses visualization to organize and recall information.
I have personally used this technique for my own PMP Exam preparation and it allowed me to recall every single ITTO without fail at the time. I didn't need to write down a single ITTO on my brain dump, because I had them all committed to memory. All of them. Perfectly!
I plan to include a section about The Method of Loci in my upcoming eBook on how to study and memorize ITTOs.
The great thing about the Method of Loci is that it allows you to memorize anything and everything you need. Not so good is the fact that it takes a decent amount of effort to memorize all 500+ ITTOs from the PMBOK Guide - and of course, you "only" memorized them. You haven't necessarily understood them.
So my recommended approach in the eBook will be that this is a great technique for memorizing "stuff" that does not come easily to you. First you should try and understand the concepts behind the ITTOs. This will be of more value to you in the long run for your career. But for those things that do not come easily to you (i.e. Table 3-1, certain formulas, or ITTOs from specific processes) I recommend using the Method of Loci.
In conclusion: This is an absolutely great technique for PMP Exam preparation, as long as it is not your primary technique but is instead used when necessary and appropriate - and it is up to YOU to decide when that is the case.