There's a simple check to see if your iron is extending past the sole, simply
flip your plane upside down and pass a small block of wood across the sole past
the iron. You will be able to hear and feel exactly what portion of the blade
is doing or not doing the cutting and have a relative sence of how much.

If that's not it, closely inspect your work in case you're planing it away from
instead of toward flat. After that I'd straight edge check the sole of your
plane.

David




I find I get 3-4 good minutes of shavings at a stroke every 5-8
seconds, and then I need to advance the blade just a fraction to keep
shaving.