I was wondering how long I will use my toks car before I will begin taking it for complete engine servicing (e.g. changing of rings, e.t.c.)? If u have any useful advice, please help.

Depending on how many miles it has on it now, and how the previous owners had taken care of it; most cars will do 200,000 miles easy.
If you want to get 6 good years out of it now do a thorough inspection and follow maintenance schedule.

Check all your fluids and drivetrain, then change oil and filters at regular interval of about 3,000 miles(5000 km)

Sultaan said it best. It depends. Also, it may be cheaper to buy a rebuild engine than to try and service it your self.

@ sultaan: Thanks so much, bro. De car has done about 198+K on de mileage. Hope it can give me additional 100K?

@ ajileko: My regards, bro.