The following happens very often :
dead drawn position
A proposes draw
B blunders (the psychological pressure, trying to force the win etc...)
Draw proposal should no longer be valid.
Another variation :
A plays a much stronger opponent and proposes draw in total fairness after an equal line opening
B blunders many moves after (gives the queen on move 30, misses a mate in 1 threat etc...)
B just has to call draw before A moves.
I still believe 3 proposal per game is fair.
dead drawn position
A proposes draw
B blunders (the psychological pressure, trying to force the win etc...)
Draw proposal should no longer be valid.
Another variation :
A plays a much stronger opponent and proposes draw in total fairness after an equal line opening
B blunders many moves after (gives the queen on move 30, misses a mate in 1 threat etc...)
B just has to call draw before A moves.
I still believe 3 proposal per game is fair.