I just replaced the OEM right front head light bulb last week. It had 2,030 hours on it. We turned the lights on when we bought the machine in June 2004 and they've been on ever since. It gets used for chores at zero dark 5AM every single day. We had one bulb burn out in the accessory work lights we had put on it when we bought it. That happened last year.
From the pictures, heat seems to be related to failure in some circumstances. If that's the case, putting in a higher wattage bulb than stock doesn't make sense to me unless it's required to perform some task that can't be performed with the stock bulb. I can't imagine what that task would be - we use ours in the dark every single day, twice a day this time of year, with stock bulbs. A higher wattage bulb will run hotter in the same environment.
My inclination, if I needed more light, would be to adapt some LED work lights to the machine. Their are versions of those that are really bright and quite energy efficient.
Fitch