In my home, I have a total of 103 x MR16 halogen downlighters. They’re all 20 watt bulbs – for the extra power, 50 watts doesn’t seem to actually be 150% brighter, and so 20 watts is adequate. In 5 years, only 4 bulbs have needed replacing. The secret? For every 2 x 20 watt bulbs, I have 1 x 60va transformer. Simple. Each transformer is under-loaded and it works like a dream.
When LED bulbs become much cheaper, we’ll probably switch to those, but currently it would be a very expensive investment! (and would require all the transformers to be replaced!).