I would want to change it every 80k or 3 years, whichever comes sooner.
The mitsubishi timing belts are perfectly fine. When it comes to spurious belts, gates is the only brand I trust. Chinese belts may be fine, they may not but usually you get what you pay for. An extra 50 dhs for a quality belt is nothing compared to maybe 1500 dhs for head rebuild if a cheap unknown brand fails.
Cost just depends on which garage you choose but again, you get the quality of work you pay for. A more expensive garage is more likely to clean things and put them back together properly whereas a cheap garage is more likely to just stick silicon on everything to hold it together.