"I have visited serveral houses and sometimes the pins feel lighter than normal. Then you goto other houses and the pins feel like they weight is heavier... Any ideas and why this happens or is this my imagination..."
Also as pins get more use, their bottoms get chipped and rounded, and so they fall more easily. If you get a new set of pins (they usually look much whiter and brighter) & if they're the same type as you had, they'll fall with more difficulty because the bottoms are totally flat.
ALso different houses have different depth gutters and have different degree of "bounciness" to their side boards. This affects pins' ability to stay standing or fall more easily. More shallow gutters make pins bounce out of the gutter more easily. It's hard for pins to bounce out of deeper gutters.
"None are so blind as those who will not see."