Yeah, Theta vs Delta gives a glide slope of stock price change needed to, at a minimum, maintain value. If that becomes greater than one's expectation for the stock performance (over allowable time frame), it may be time to exchange positions.I was actually musing over this the other day, thinking there might be a good exit-strategy rule of thumb based on some of the greeks.
For e.g. we know for a long option, Theta starts negative and continues to decrease as you approach expiry and the intrinsic value falls. And Delta starts positive, grows as an OTM option approaches ITM, or falls as an ITM option approaches OTM. So there may some sort of signal one could derive when Theta grows larger than Delta times the average daily Drift... which would be something like a proxy for the average expected daily change in an option's value.
However, it can also be indicative of a higher return position if there is a spike in the preferred direction.