Domain aging factor helps your site ranking over SERPS of google for instance, but does not help developping the pagerank of one site
Punishing sites for changing their design / improving SEO is stupid. But if you need to think that to sleep better at night, go ahead. How many design revisions do you think Google will save? One? Two? Three? "We just did a redesign and had to change the design again, now we dropped off the first page. Whoops." Wake up.
I can only say this. Since chanting my domain name a few months ago I finaly got a PageRank of 6 and before it was nothing. The only difference I can see is gradually putting new arterioles, posting articles in article directories aggressively, buying links and links people added to my site with no effort on my own. I also tried automated article summation. Having said all that I am not sure if any one of those efforts brought my PageRank up or not. At this point it looks like the thing do is to do all of these methods over time and there may be good results. At least it worked for me.
In the past I've read various SEO articles that claim registering your domain for a longer period of time will give you better ranking which would make sense but here is the problem I see with that..... How would google know how long I registered my domain for? They aren't a registar (are they?), and I don't think they can be looking up each and every domain on the internet with another registar so how would they could they possibly tell how long I've owned my domain for or how long it's registered to me for? Or am i missing something?
begin and expiry date of all domains are in public records such as whois and these data usually can easily be queried by tools if needed for a particular reason. hence Google or any other SE COULD check the age and expiration dates of any domain and take such data into consideration check it yourself - if you have Linux run whois yourdomain . com or /usr/bin/whois yourdomain . com to see what others can see of course there are a number of domains with blocked data - as a general rule those hiding their data are in my opinion suspicious for potential monkey business or illegal business and I would never do any kind of transaction with such domains - Google as well could tag such domains if needed hence NO need to be registrar to have access to domain owner data ALL world can see all they need if they want and know how to