Now that I have decided I will be 25 for the rest of my life, it's important that I keep up with what the kids are into. But I felt like a real failure when my short attention span and general busyness prevented me from appreciating that 90210 was coming back. Yeah, I'd seen the ads and heard rumors about the return of Brenda, etc., but it hadn't really set in what this all meant. It wasn't until Sarah Morrison responded to my IM yesterday with "90210 starts tonight" that I realized I should be really excited about this. I mean, I loved the original. We even had a party…