i did grill less (well my grill holes were huge and no cloth) for almost 6 months without problems while using my he500 for 5 hours a day at least! and this is what i did to keep them in good condition:
..u just have to keep them save from dust when not using (most part of the day)..so this was my daily routine...very easy!!
1. put them ALWAYS in a bag or in a desk draw (dust free ofcourse!) after use,
2. brush ur hair before u put them on so u get rid of ur loose hairs
3. clean the pads with ur fingers a bit...u will be surprised how much hair/dust there is on them (especially the velours ones)
4. and last many people forget..if u use a comfy chair on which ur head rests...tab that a few times to loose the dust and ur hairs of the other day
and ofcourse ventilate ur listening room regulary and let vacuum a bit...
thats all! easy peasy
and it helps if ur house is practically dustfree and has low moist levels ..like i have here