It does take alot of time to make games on Amiga... some of my AMOS projects took anything from 6 months to a year or so to complete.
My current project (made in assembler) has taken me erm... I think 3 years or so thus far (6 months to create level editor in AMOS, 6 months to create raw sound editor in AMOS, 6 months to learn how to decode .png files without using the png.library - I wanted to do it properly
and the rest of the time was used to draw graphics and code the program).
I'm at the stage where I need to tidy up the front end (title screen), add sound and draw yet more graphics before I'll be in a position to maybe(!) release a demo...