Well now.

I started collecting cels as a portion of a REAL 
mid-life crisis (I'm 44 and darn proud of every 
stinkin' white hair merging with the brown ones, 
thank you very much).  Like you, I often consider 
whether the money I've spent on cels, posters, 
figures and conventions in the past 2 years could 
not have been better spent on things like new 
carpeting, and so forth.  

What it comes down to for me is this:  do you 
love the cels for themselves?  I only own about 
two that I would even consider parting with.  
They are physical representations of special 
moments I've spent with characters I love. They 
are artifacts of myself in the same way that 
photographs are...tangible reminders of special 
moments.  They're also beautiful.

So... if you're collecting cels as an investment, 
I'd say that maybe your money is better spent in 
stocks.  Doesn't sound that way to me, though.  
It's like anything else in life; that initial 
burst of enthusiasm is bound to wear a bit thin 
at some point.  Then you know whether it's 
something you really love, or just a fun passtime.

Probably made no sense at all...but I'm in the 
middle of justifying my existence for the past 4 
years (post-tenure review time)