As such there is no limit on the amount of information that can be saved in a Session Object. Only the RAM available on the server machine is the limitation. The only limit is the Session ID length(Identifier) , which should not exceed more than 4K. If the data to be store is very huge, then it’s preferred to save it to a temporary file onto hard disk, rather than saving it in session. Internally if the amount of data being saved in Session exceeds the predefined limit, most of the servers write it to a temporary cache on Hard disk.
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</> MV Techbytes 
RAM is also not a limit, as most of the server can store more information in session than available RAM, as they store the session in temporary file serialize/deserialize as required.
However it is not gud practice to store that much information in session.