Outer Limits 4x4 Board

Gday again, i have noticed that when i have been working the V8 a bit, it gets a little more difficult to start (3 to 4 seconds) as opposed to 1 to 2 sec when it is cold. I notice it more so when i stall it in tricky situations and usually it has been working pretty hard, but also when i have been towing and stop for fuel, sometime it may have been sitting for 10 to 15mins and still more difficult to start. It never used to do this but has started this recently.
Any ideas as to what would cause this? Just seems odd that i can leave it for 2 months without starting it and it will start after about 2 sec but longer when it has been working.
Was thinking of replacing leads and plugs as a start.
cheers

3.9l V8

Could be your ignition module on the dizzy.Once they are on there way out they start to do things like that when it gets hot.Becomes harder to start.