So how long should your irons last..
I brought my MP32 irons at the start of last year, second hand, but in decent condition.
Fantastic set of forged cut muscle irons. Problem, as you say, forged clubs do tend to wear a little quicker than cast. I use my previous R7 irons as an example. When I sold them there was hardly any wear for a club I'd had and used 3-4 times a week for 12 months.
I practice quite often, around 3 times a week, plus 18 holes in a Saturday. When I had the clubs there was a small amount of wear around the sweet spot (Penny) that wasn't too visible but after a year of regular use they are much, much more pronounced.
My PW, which sees quite a lot of use is hammered!
I think these irons would have lasted me at least another 18 months, but then they would be well worn.
I had a windfall and weighed up the options. In 18 months time, would I be in the financial situation where I could afford to replace a worn set, chances are probably not.
I've replaced my irons (.... And pretty much my whole bag aprt from putter) this week, but will not be upgrading again until they are in a worse condition than my MP32's were in when they were replaced, so, 3-5 years seems about right.
Now ask the question as to why people replace their driver or putter so often and that's definatley a different story.