I would starve playing only one tournament at a time, that's why life poker for me is not an option. It doesn't really matter over how many days, some hours would be enough.
Two to four tournaments at the same time is fine, it's enough action not to get bored and still enough freedom to do something else while playing. For example being active in this forum, reading news, watching clips or poker educative material.
When, for what reason ever, I have to play one tournament at a time online, I usually play computergames like path of exile while folding 😁