I'm getting my first second wheelset, to be alternated with the stock
wheelset on my bike. The cassette on the old wheelset has about 2500
miles on it and seems to be in pretty good shape. I plan to swap the chain
out for a new one. My question concerns what to do about the cassette.
It seems that I have four options:

1) Get two new cassettes, one for each wheelset.

2) Leave old cassette on wheelset 1 and put a new one on wheelset 2.

3) Get a single new cassette and share it across wheelsets.

4) Share the old cassette across wheelsets.

I'm leaning toward option 2). I don't like options 3) and 4) too much since
they require removing/installing the cassette every time I change wheelsets.
Option 1) is ok but I think that the old cassette still has some miles left in it.

Is there any significant reason *not* to go for option 2)? Would using an old
cassette wear the chain down more rapidly, leading to wearing out the new
cassette on the other wheelset? Do options 3) and 4) have any merit?

Thanks!

Sharing casettes gets to be a pain, and at least partially defeats the purpose of having extra wheelsets, being able to swap quickly. Technically you probably would increase the wear slightly by using an old one, but I doubt it would be enough to make a significant difference. I don't really keep track of cassette wear, but I know I have some with a lot more than 2500 miles on 'em.
You should be aware, though, that I don't spend much money on stuff like that until the pieces actually fall to the pavement during a ride.

Definitely #2 - swapping cassettes really isn't that big of a deal, but having to do it everytime you swap wheels is more trouble than you need.

But really, I'm interested - what's the 2nd wheelset for? Different types of rides, terrain, racing? If so, give some thought to the cog combo - maybe a different combo would be more optimal than what you've already got. As an extreme example, I have more cassettes than wheelsets - separate 12-23 cassettes that stay on my training wheels and race wheels, but also a 12-25 for particularly nasty hill races and an 11-23 on my TT wheels.

Thanks for the replies.

The new wheelset is going to be a bit lighter than the first, for faster group rides.
I just do recreational riding. I don't race and don't plan to start anytime soon.
The older wheelset will be my "training" wheelset - whatever that means for a
recreational rider :) I was thinking of going with a 12-25 cassette but I'll give
that some further thought.

Definitely #2 - swapping cassettes really isn't that big of a deal, but having to do it everytime you swap wheels is more trouble than you need.

But really, I'm interested - what's the 2nd wheelset for? Different types of rides, terrain, racing? If so, give some thought to the cog combo - maybe a different combo would be more optimal than what you've already got. As an extreme example, I have more cassettes than wheelsets - separate 12-23 cassettes that stay on my training wheels and race wheels, but also a 12-25 for particularly nasty hill races and an 11-23 on my TT wheels.

That other post made a good point, and it's worth considering. I have a Rivendell Atlantis, a sorta-heavy "all around" frame I really like. Since I use it for all kinds of riding, I have a fairly light wheelset (reasonably light--I weigh 230, so it still has 36 stout spokes in it) with an 11-26 cassette, and a stronger, wider one with a 13-28 and 700x35 Paselas. A one-minute wheel swap really changes the feel and capabilities of the bike.

Yes, great points. Since the rides I usually do don't vary too widely in terms of
topography, I'll probably go for fairly small differences between my two wheelsets.
I'll continue to use 25 mm tires on my training (old) wheels, with a 12-25 cassette.
For my new wheels, I may try 23 mm tires and an 11-23 cassette instead.
Thanks again for your input!

That other post made a good point, and it's worth considering. I have a Rivendell Atlantis, a sorta-heavy "all around" frame I really like. Since I use it for all kinds of riding, I have a fairly light wheelset (reasonably light--I weigh 230, so it still has 36 stout spokes in it) with an 11-26 cassette, and a stronger, wider one with a 13-28 and 700x35 Paselas. A one-minute wheel swap really changes the feel and capabilities of the bike.