Sure you can, but it is neither a boeing recommended SOP anymore nor is it really necessary as the system does it and shows the result on the display system, it even shows if it receives DME only or VOR information additionally.
PS Where did you get 'higher' and '30 seconds' from........................?
ATPL 101 and recently during re-studying the route manual somewhere. As posted above the ident tone for the DME is around 300Hz higher than for the VOR/ILS information.