My first, and current, homebrew world is slowly being built, and this is happening alongside my group playing through it. Because of this, Character base for the Party was created out of the core DnD races/classes, rather than being homebrewed at all, and as such dwarves and elves existed with their super long lifespans. Whilst this has little effect on the game in general, it does start to bring up questions when I'm talking of events that happened 400 years ago and Characters remember being there. My world has an almost fully integrated societal structure (mostly) where dwarves, elves and humans co-exist, along with various regional races and other creatures. The various groups relate more to regions, countries, clans or families than they do racial structures. However, this brought the issue of how friendships or political structures would exist when you have people who have outlived a humans grandfather and will continue to outlive their grand children.
So, issue at hand is whether or not I reduce the livespans of everyone. I figure this is the easiest way, and will break down the barriers between the races even more. Why not have a dwarf and a human who are kids together, adventure together and die old together? There can, and will, be exceptions, but I feel like this would be better suited for a very short lived Katterfolk colony in the far North, or a very old lived Lizard race in the depths of the Ban Molok jungles, rather than entire populations of wide spread races. Can anyone see any issue with reducing these lifespans, outwith of messing with classic DnD timelines and lore?
Changing the lifespan of those races doesn't change too much. I think there is the way that those races view things is the classic thing you think of changing. Like an elf taking years to build one thing wouldn't matter to said elf if they live for hundreds of years, but that may be less likely if they have a shorter lived life. The other factor that I think makes this matter less is that they are living in communities with the other standard races.
Just thinking of what defines the races and if that changes based on a shorter lifespan would be the only question I would ask as things come up in your world.