Pippen, you get a big THANK YOU from me for at least noticing they are 'big talkers'.
I often end up with darling older couples in my office (at tax time) that truly look forward to seeing me each year. Some of these people have been with my firm since they filed their first return, opened and closed their businesses with us, and now I'm doing their fairly simple return for a little retirement income. One in particular, the return takes me only five minutes. I book and hour and a half to see the client because of the conversations. I remind myself when I'm hearing the gross details of a knee surgury or grand baby's potty training that I owe the client the respect that comes with doing decades of business with my company. I can tolerate a LOT of 'small talk'. So on some level, the professional owes you some face time just for being the customer. Some times a new client is just trying to find common ground as most people seem a little intimidated at first by taxes. Plus most of us accountant types come off as a bit grouchy when really we are just in deep thought. Any professional worth his/her salt knows how to reel these things back to the business at hand and how to close the deal. I have one client who was born in a far away country. I could listen to him tell me about "the old country" all day, so it maybe the professional really just likes your parents. =)
Also, I'm an exception in my industry as I don't bill by 15 min. periods. Perhaps the lawyer didn't mind taking up his day with small talk as he'd bill for all time spent with client, not just time used for matter at hand.
If you are their ride, then you simply must insist that you have to xyz at such and such a time. Begin leaving 15 mins prior to when you have to, and just don't shut up about it. It seems strange that to stop other talking you have to out talk them. Politely, of course. You just have to be determined no one will bean dip you from the course of leaving. Most professionals will help you with this. I'm surpised a busy professional would say "oh I dont' mind another story!" Usually if an adult child or care taker is kind enough to open this door for me, I jump thru politely with both feet - "oh, as much as I'd love to hear about your neighbor's dog's groomer's trash mans' new house's tile grout choices, (adult child) is correct, we don't have much time, so let's go ahead and discuss these stocks you sold for a big profit this year......"
If you are not their ride, it is still the same solution. Sign what you need to and get out. Most professionals have fail safes to get rid of long winded clients (I know my direct boss's client list so well that I know when to trigger the 'alarm') Every office has a different 'alarm', but all of the ones I've worked in there is always one person that knows how to make a call from a break room phone to the front desk, thus resulting in saving a partner with an "emergency call from out of town". Or whatever. One firm I worked at we only used the 'alarm' when told to, via a private message to our personal workstation computer that would tell us when to come into the senior partners office and what to say, etc. to clear the room. However, this was only after the senior partner had determined enough time had passed for a heafty bill. He knew he couldnt' get away with billing people for 2 - 3 hours of 'small talk'. Depending on your parents relationship with the service provider you might mention how billing usually works (be careful here as I had a rather rude adult child say this sort of thing to her very sweet mother. I didn't care for the grown child or how she spoke to her mother, especially about how she couldnt wait until she was dead so she could have at her money. I happily exclaimed that of course my firm does not bill Mrs. Sweet Lady by time, she had a flat fee of $35.00 for 1040 preparation each year and her bill had not changed in ten years and would not be changing. Adult daughter was really mad after that as I knew what she was paying at another firm for tax prep and hers was easier than her mom's. Adult daughter had already been fired from my firm.)