When you buy a new wheelset, would anyone recommend getting a new cassette and chain?
or
Just use the existing one?

The existing cassette still has life....but my thought was that I should just replace it and the chain, that way all the components are on the same mileage...

Let me know your thoughts

Not necessary. Wait til the cassette needs changing.

If there was any logic in what you are proposing then you would have to replace the wheel everytime that you replaced the chain and/or cassetee. Nobody would ever consider doing that. What prompted you to consider this in the first place?

No need unless the cassette and chain are worn out.

In that case you probably want to change the chain rings too.

If you're going to use the old wheelset as a backup, then it's quite handy to have a cassette for both wheelsets. (and pretty much essential if the backup wheels are going in the wheelpit in a race.)

It also gives you the option to use different gearing for different terrain, different circumstances.

I'd buy a new cassette for that reason.

+1 for merlinextralight's suggestion. To your earlier comment though, a chain typically lasts a much shorter time than a cassette, as mentioned multiple times elsewhere here. If you want to be kind to your drivetrain, be sure to change your chain before it gets too worn/stretched.

here is my "logic"......I bought my bike used...its an 07, and didnt have alot of miles.
I purchased a new wheelset, and am getting ready to put them on the bike, then I thought about the cassette and chain and maintenance.

Since I dont know the exact mileage of the old cassette and chain I figured when I put the new wheelset on, I would put a new cassette and chain on. That way, I know the EXACT mileage on each component and can keep track with maintenance...extending the life of ALL three components.

I'm not a moron and would not consider replacing the wheelset EVERYTIME I changed the cassette and chain......that's not what I was asking.

You don't need to know the mileage to know whether the existing chain and cassette need replaced.

Measure the chain for stretch, actually wear. If its "stretched" beyond 1/16th of an inch replace it. (See Sheldon Brown's or Parktool's website)

As for the cassette, replace it when it skips, or the shifting performance deteriorates, even when everything is clean and adjusted.

Thus I'd measure the chain. If it needs replaced, replace it. Once the new chain is on, the cassette will tell you whether it needs replaced.

Awesome...thanks for the advice! Really appreciate it.