its a harsh consequence to be considered "dead" for that system you fled from. - but there would be trouble with re-engagements if there wasn t that rule. ... frankly, i think it shouldn t be 4 hours, but rather a "fair amount of time" - whatever that would be.
but as you cannot make each player him/herself consider what a fair amount of time is ... we got the 4 hours to be fair to everyone.... but look at the bright side..... when the opponent leaves that system, you are free to go back.