When the progressed sunsign changes, lifestyle changes. But what changes when the progressed planets change sign? I checked my own Mercury and Venus in progression and this is what I found:
In 1971 and 1995 I had a Progressed Mercury Return. In 1981 the progressed Mercury stopped retrograding and went direct, just before the square with Saturn. I recall that year and the decission that I didn't make. I remember 1995, because that is the year that I got a teacher's license. But I don't know about 1971.
I think that Progressed Mercury conjunct Mercury doubles your interests and study results. And I think that when Mercury returned to the natal position (in 1971) I started to make my mind up, again (new ideas, new interests, new opinions). In 1995 the period of studies ended and a new period began. I remember that I couldn't read books in 1995/1996, because I had read to many of them (and to quickly) in the years before.
I know a person who experienced a Venus return in progress (progressed Venus conjunct natal Venus). That doubled his sympathies so much!:) He started to live with his mistress and didn't divorce. So this also doubled the number of wives!
Mercury and Venus also may change sign in the progressed chart. My Venus changed sign from Sagittarius to Pisces and if I live long enough I will see Progressed Venus on Zero Aries. But, in what way has it changed my style, preferences or hobbies? Venus progressed to Pisces in the summer of 2001 and I don't remember what exactly changed. In 1976 Venus progressed to Aquarius and I don't know what happened. It was one of those years that pass bye...
In June 2010 my Mercury changed sign to Aquarius. In 2010 my website got a new style. I don't think that I had a mind changing experience in 2010, however.
So, maybe there were subtile changes, but I can't see in what way the changing sign of Mercury or Venus had impact on my life, my preferences or my mind. Since of few years Venus is in my first house. I will ask if people noticed this beneficial influence on my presentation!:) Seriously, I think that the change of sign of the progressed Mercury and Venus simply contribute to a general picture of change (if it is there) and not much more. But if you experienced major changes, please let me know!
This month January you find a lot about progressions and the progressed chart on Astropost.
Also visit: Astromarkt.net for example about Mercury and aspects.