I've not experienced my N7 getting bogged down after nine months of use, like a PC after a few years of use, where it seems to inexplicable slow to a crawl. Perhaps if I give it time it will, but for now it hasn't happened.
However, it does get slow at times for reasons I do understand, but hopefully will be improved upon in the next gen N7.
Start up time from power off is extremely slow. Even after it gets to the home screen, it takes a few minutes to settle down and be fully responsive. This is because I have a ton of apps fighting for precious resources to start their processes and get connected to the internet. Once everything has settled in it runs smoothly, until...
My N7 bogs down when there is a heavy load on WiFi. If something is downloading in the background, or a big web page is loading, or video is streaming (depending on the source), the N7 will often struggle to respond to touch and performing other activities. I find this to be especially true while doing app updates and installs. Even after it's finished the downloads and installations, the N7 is very slow for another minute or two, as it is perhaps updating databases, etc.
I also find that it doesn't handle streaming video and using a Bluetooth headset at the same time, as the video stream sputters quite a bit. Disconnecting Bluetooth resolves the problem, as it frees up WiFi resources.
So, to resolve the above issues, do a couple things. First, don't install any additional apps on your N7, allowing start up times to remain acceptable. Second, don't use WiFi. This will keep the WiFi activity from hogging all the resources and processing power of the N7 so that it doesn't slow to a crawl. Also, change its oil and air filter on a regular basis.
Either that, or use your N7 like a normal person and understand its limitations. And hope for improvements in this area with the next gen N7 this summer.