On cutting the tops...
Deer browse seng all year, starting in the spring, thru fall... in years when it is very dry they seem to hit the seng a lot harder.
A top from a mature root, sometimes they will skip a year or two and not even send up a top. Not sure why they do that but it is a fact, it happens.
On roots that are quite young... 2-3 years old, losing the top early in the spring, would be more serious (set back) than it would be for a mature root. The top is what is used to build up that root, store energy in it, etc...
If you cut the top off a very young seng plant (2-3) years old... 2-3 years in a row (early in the spring, april, may)... it may just expire and not have the root strength to send up a top the next year.
If you waited until August, September to cut that top off, the root should be just fine.
On mature roots, it should not be a problem (or set back at all for the plant/root) to remove the top as long as you want until July/August to do that.
When i first started planting stratified seed, I had some first year 3 leafers where the top died back late June, and when I checked those beds the next spring, the majority of those came back again. My seng is up in early April normally... so with a little more than 2 months (around 70 days) of growth, the top was able to store enough energy in those tiny new roots, so that is sent up a top the next year.
TNhunter