You also have to take into account that the Indian Air Force has an extremely high op tempo with constant combat air patrols in very very rough conditions. Also, thier pilots are considered to be some of the best trained amongst the non-western nations, with a very competitive selection process and a high porportion of them holding advanced technical degrees in engineering disciplines.
Spare parts are not really a problem, as they long ago aquired the capability to indigenously manufacture most of what they need for thier older aircraft. However, any time you have aircraft that old in constant use youa re going to have crashes and failures. You would be amazed at the number of catastrophic failures that occur in US military aircraft every day. Luckily we have the funding to throw a LOT of money at our aging fleet to keep them running.