Specifically I am talking about Legos that you open up and build and then are ready to pack them away after displaying for a while. Is it best to completely disassemble them before putting them away? Generally in the past I only take it apart just enough so that it will fit back into the Lego box, but still leave most of the parts assembled in case I want to display it again in the near future and not have to reassemble the whole thing. But my question is does it hurt the bricks at all for them to remain assembled for long periods, even years at a time? Does it tend to affect the tightness of the bricks in any way? I just want to know if I should be completely disassembling them for long-term storage or if it even matters.

I know large sets have a tendency to sag over time when built, but how much will it effect individual bricks is hard to say. I wouldn't think it is a big deal.

I know that Legos are designed to be extremely resilient and are supposed to be able to survive for years on end in a sunny display box. Not that the pieces won't yellow after 10+ years, but they are very durable. That is why we still see 1950's Legos on eBay today. If you have the room (which it sounds like you do), its fine to display them out for long periods of time in "built mode". If not, I would put them in resealable baggies and then put the baggies into the original box along with the instructions. Just because if you keep them in large chunks of pieces, it makes making sure that all the pieces are there in the future alot more difficult to do. Also, if you ever plan to re-build you set, its never fun to hurt your fingers prying apart Lego pieces. Saves you alot of trouble in the future. XD

Specifically I am talking about Legos that you open up and build and then are ready to pack them away after displaying for a while. Is it best to completely disassemble them before putting them away? Generally in the past I only take it apart just enough so that it will fit back into the Lego box, but still leave most of the parts assembled in case I want to display it again in the near future and not have to reassemble the whole thing. But my question is does it hurt the bricks at all for them to remain assembled for long periods, even years at a time? Does it tend to affect the tightness of the bricks in any way? I just want to know if I should be completely disassembling them for long-term storage or if it even matters.

Not sure If it matters how you store older elements. Some of my light gray bricks (from the mid-1980s) discolored over 25 years despite being packed away from light and dampness in their original boxes. The only elements that discolored were mainly 1x2 and a few 1x3s.

The bricks still connect tight to each other as before.

I generally disassemble them and then inventory them to ensure all the pieces are there. Then I place them in ziplock slider bag. They are less likely to open in storage. I store the books and boxes separate. Since most of the newer boxes can be broken down flat it makes for better storage and more room. Since its already been opened I don't worry bout cutting the seals on both sides. If I ever want to build again ill just get the book and find the bag in one of my storage totes.

I've got plenty of storage room in my garage for my lego sets I'm planning on selling in 1-2 years. However, I'm in southern CA and have hot, dry heat in the summer where the garage may reach 105-110 on the hottest days of summer. Can this cause a problem for these sets?

Yes heat can make seals burst. I'd get a climate controlled storage unit out there if I were you

I've got plenty of storage room in my garage for my lego sets I'm planning on selling in 1-2 years. However, I'm in southern CA and have hot, dry heat in the summer where the garage may reach 105-110 on the hottest days of summer. Can this cause a problem for these sets?

Way too hot for your sets buddy........it would definitely ruin them.