There is no "right number" of Svchost.exe processes per se'.
The Svchost.exe file is located in the %SystemRoot%\System32 folder. At startup, Svchost.exe checks the services portion of the registry to construct a list of services that it needs to load. Multiple instances of Svchost.exe can run at the same time. Each Svchost.exe session can contain a grouping of services, so that separate services can run, depending on how and where Svchost.exe is started. This allows for better control and easier debugging.
The following MSKB articles explain the Svchost.exe process, and may help you to understand why there's normally multiple instances of it running at any particular time... A Description of Svchost.exe in Windows XP...
I had some problems with "scvhost" = virus (not svchost) and since then I'm obsessed with any file that looks like it.When I saw 5 processes of svchost I really wanted to know more about it.
Anyway,thanks for infos.