Long term impact of swarms issuing from a parent hive

[BEE C]

I was wondering about the impact of swarms on the health of a parent hive that throws swarms throughout its "life".  What do people think?  I have yet to read about the impact of swarming other than on that years honey harvest.  If a swarm is a reproductive swarm thrown because of a hive being vigorous, and is a natural process which helps to further the species, is it depleting of the parent hive? or...? Does swarming shorten the lifespan of a hive? Of a queen? 

Second question.

Do hives need to be requeened for reasons other than to keep a hives "production" surplus for the bee keeper or can hives replace a queen on a consistent enough basis to naturally allow them to do so?  How many of you do this, leaving the bees to requeen as necessary? If so, do you find they do so well enough to stay healthy?  Those of you who requeen, do you do it to keep honey surplus at a reasonable level? and have you had experience of a hive crashing because it was not requeened?

My first two hives are in their second year, and I was thinking about requeening in the fall if the bees hadn't do so already.  Both queens are producing nice full frames of brood.  There are approximately twelve frames of brood in various stages from hatched to sealed in two brood boxes.  I didn't use queen excluders so there is some frames in each hives bottom super that have a bottom half brood, but Im happier with that to reduce hive congestion.  This is the beginning of our main flow, about a week in, and honey is coming in filling one super and filling half of a second.  Im building out small cell from starter strips in both the brood boxes and supers so they are having to produce ten frames in each hive.  Both these hives were split out early and requeened with "Hawaiian" queens, which are completely golden with no black markings. 

I would really appreciate any suggestions, as to whats worked for others or what peoples views on this stage on my hives, as this is only my second year and have always found good advice here.  Thanks.  Steve