verb plain koto mo naidehanaika = don't need to do it / don't need to force/push myself / yourself to do it,
This phrase implies the meaning of 無理して(ムリして)and is used with/ without the word ””無理して".
(無理して)長時間がまんすることもないではないか。
I / you don't need to force/push myself / yourself to endure for that long.
(無理して)食べることもないではないか。
don't need to force myself/yourself to eat it.
========Please compare with "ka" and without "ka".
verb-plain koto mo naidehanai ka = I/ you do not need to force/push yourself / myself , Don't you need to~
食べることもないではないか。= do not need to force/push yourself / myself to eat it
verb-plain koto mo naidehanai = Sometimes you/I do it.
食べることもないではない = I eat it sometimes (although it is very occasionally.)
I think that it is well known about Japanese uncomfortable crowded train.
Japanese commute to work on a crowded train for one or two hours. It is average commuting time.
There is nothing you can do on the crowded train to comfortable yourself. You just have to be patient with that uncomfortableness.
If you have to commute to work, this is what you have to do.
However, if you work at home, you don't need to commute, If you don't commute, you don't need to endure that uncomfortableness for the long hours (communing hours.)
In the sentence "長時間がまんすることもないではないか。" , "uncomfortableness" and "commuting time" is not mentioned, however, from the word "満員電車”, it is understood what Shinichi is talking about.
So,
長時間 denotes the long commuting time
(不快さを)がまんする to be patient / to endure (the uncomfortable)