Probably its some bollocks about getting someone to pay to get a new light approved. They really are ****e though.
so is there a mod we can do to increase their life
Not really its the hot cold cycles and high temp which kill them quickest which is maybe why they die so quickly in a training environment. Every student checking they are working, then off and on depending what the local procedure is. Having them on with no airflow over them really screws them so if people turn everything on then take 10 mins doing a walk round its probably worth about 10 hours of flight usage.
If you look at the box they come in I saw one that claimed 100 hours. Its lasted 15 hours of night ratings and cost 50 quid to supply and fit and to be honest they were only really on for the solo work and taxi and a couple of circuits for each student. So worked out at over 5 quid per hour of usage. I can really understand why owners don't want you using them. If you feel you must use them turn them on at 500ft leave them on, then turn them off either on short finals or on the roll out (much as I hate saying that because I don't believe you should be doing anything until you are clear of the runway).