Star99,
I'm using 2001 FB15 ExSaloon Manual car for last 3.5 years and never had major problems like sensor issues or any Engine or suspension issues so far. It depends on how you treat and maintain your car. if you treat her well, she will give her the best in return.
Sensors - As i know, 2000 FB15 had this issue and has been fixed in later version. Ripper > correct me if im wrong.
Hearing all the Cranky noises - I don’t know what you mean by this, I normally drive to Middeniya, (Via Rathnapura, Embilipitiya) once a month and i never ever heard any unusual noises like you said.
Fuel - I do nearly 9-10KM in Colombo and 12-13 in Long Run *(with AC).
Durability - FB 15 is not a Sports Car or something like that, and does not have Boost or anything . You need to be very gentle and smooth when you drive this type of cars and that will help you to increase the fuel.
Common thing is what ever the vehicle you have, it needs proper maintaining, and changing oils, tune-up etc needs to be done at the right time. No matter how long you use it, if it’s in a good condition, will keep the re-sale value in a good level.