From http://www.chabad.org/library/article_cdo/aid/144573/jewish/Three-Weeks.htm , one learns that one should not taste new fruits during the three weeks in order not to have to say shehecheyanu.
During this period, we lessen the extent of our rejoicing. We don't:
Recite the Shehecheyanu blessing. Thus, we do not wear new clothing or eat fruit which we have not yet eaten this season so that we will not be required to recite Shehecheyanu.
It appears to me that this prohibition also apply to blessing over old friends.
The Talmud teaches that one who hasn’t seen a good friend in over a month should recite a special blessing – the shehecheyanu blessing- upon seeing them again. A “friend” in this context refers to a person with whom one is exceptionally close, and whose presence brings one great happiness. In the event that an entire year has gone by since one last saw such a friend, one recites the blessing “mechaye hameitim“. Similarly, one also recites the shehecheyanu blessing when being personally received by a great person, particularly a renowned Torah scholar, who is rarely accessible for private audiences.
Should one go out of one's way to avoid seeing good friends one has not seen in a long time during the three weeks and/or nine days?