Definatley not, if you do you will lose all access to archive explorer and search.

What you need to do is to either extend the exisiting index volume or close the exisiting index (that way no new records will be added to it) and then create a new index volume and assign it to each of your archives.

Here is a technote that describes the process you have to take http://www.symantec.com/business/support/index?page=content&id=TECH48906&key=50990&actp=LIST it is for ev7.5 however the process is essentially the same, just a few of the windows will look slightly different.

Let me know if you need further clarification.

1. Create  Indexing folder on a volume where you have enough free space available.
2. In EVA console, expand Enterprise Vault Servers, expand respective EV server and select services.
3. Right click on Indexing service and go to properties and then index locations.
4. Close existing index location which is running out of space
5. Click add and assign new indexing path

This will add 8 indexing folders in the given path

Note:- closing index location will not delete existing indexes (http://www.symantec.com/business/support/index?page=content&id=TECH55944)

To move indexes to another location, follow the below steps

1. Right click on individual archives, then properties and click on index volumes
2. Click on change location and select new location which is added previously as per step no. 5 above