It's impossible to answer the question without knowing more about your  
exact situation.  What areas of performance are the highest priority, how  
do you expect users to use your server, what are the relative costs in  
time and memory involved, what kind of hardware are you running on, which  
version of Windows are you using, etc.?

Now, I'm not saying you should post the answers to all those questions  
here.  I'm just trying to point out that it's a fairly broad question and  
this isn't really a great forum for answering that sort of thing.

Now, that said, I would say that in most situations if you are concerned  
about responsiveness then the right thing to do is keep your objects  
alive.  You don't have to worry about idle clients consuming physical RAM  
and thus interfering with responsiveness serving other clients, as Windows  
will swap out to disk the memory that's not being used.

Obviously there may be a concern with respect to running out of memory  
(consuming the virtual address space in the process being the most likely  
concern), but IMHO that's better addressed by other means (e.g. switching  
to 64-bit Windows if it's really that big of a problem).  Unless your  
server is serializing user access and guaranteeing that you are never  
servicing more than some fixed number of users at a time, then your memory  
requirement is determined by the total number of connected clients anyway,  
whether or not you discard service objects when they aren't needed.

Pete