Electrical question for the clever okes!

I know I will need to call in an electrician but I was hoping that someone could help arm me with the possible problem so I don't get a 'new one' ripped by whoever I use ;D I would rather tell him the possible answer rather than him telling me!
My place is 6 years old and I have an ongoing problem with globes blowing. It happens in different areas of the house but most notably in my HT room where I have a number of down lights. Some of the d/lights seem to last less than a month and it's not necessarily the same ones that blow.

Any suggestions as to what could be the cause?
Cheers