Danvzare:
Time management is the key along with enthusiasum, weather it be MAGS or other.
With MAG, as you say time is shorter...
Myself: I generally 'See' a good idea or two where I know what I want to do within minutes...
Then write the basics down.... that's about 20 minutes...
So far all within a day...
Then make/gather most of the assets.... usually within a day or two.
Start piecing them together as per notes made..
This usually takes from 3 to 5 days...
Start scripting my ideas and adding the elements, which may change a little over time...
This may take me up to 12 days allowing for extras stuff to include.
Then another day or so doing the gui's and more scripting.
By the time i get to day 15 i am generally running tests and tweaking.
This could take up until the end of the month, depending.
I find a month more than enough time....if you only do one or two rooms i'd say within two weeks.
A month is generally long enough though I have found it a bit tight on some instances.
Not saying my games would win awards but they are complete and playable.
All the more reasons for people to get down and dirty and start creating.
Long live MAG

From VampireWombat:
What if there were some MAGS starter packs?
That is a possibility, it would certainly cut the time down..