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Contrary to one of the previous answers, computers do not "need sleep." They are electronic machines and don't require being turned off in order to work well. Think - how does Yahoo Answers stay online 24 hours a day, 7 days a week? Simple, the servers that host the site are never shut off, proving that no such "sleep" requirement is necessary.
Windows 95 is an interesting situation since it has a large number of flaws that have been fixed with newer versions. One such flaw is that it has a spontaneous memory error after being on continuously for 42+ days. It's a proven characteristic, and gave Microsoft quite the black eye for a while. In my opinion, I would shut off the computer, but not for the reasons others have mentioned. Primarily - a powered on computer wastes energy. With electrical costs already very high, every little bit saved helps the environment and your wallet.
On the flip side, starting a computer from being powered-off is hard on the hardware. Things heat up and cool down during the cycle, causing pieces to expand and contract tiny amounts, which can spell disaster for older systems. This usually isn't much of a problem, but it is much more rare for an "always on" system to experience a failure than for one that is constantly being turned off and then back on every day.
Perhaps the best option would be to get a new computer that is more tolerant to power cycles... then you can turn it off without worrying about whether or not it will come back up the next time you turn the switch back on.