[Zigûr]

Regarding the danger of continuing to use the Three after the One was rediscovered, would it not have been more dangerous to stop wielding the Three and left Rivendell and Lórien undefended by them? Those were safe havens necessary to enable the Ringbearer's progress to Mordor. I believe their use was risky but that they had little choice in the matter. Regardless, as has been observed, all would have been lost had Sauron recovered the One whether the Three were still being used or not.

A situation had been engineered in the North to ensure that Sauron was incapable of deploying his full strength against his enemies in any kind of concentrated attack - he had to assault Dáin and Brand, Thranduil and Galadriel simultaneously. Without Lórien being such a difficult target, Sauron might have been able to overcome Thranduil and, as he intended, combine his forces at Dol Guldur with those of his allies in Rhûn, who ended up having to besiege Erebor largely unsupported. Sauron launched three attacks against Lórien which he must have known could not succeed simply to stop Galadriel being able to come to the assistance of Thranduil or attack Dol Guldur.

My point is that I think the Three were actually more of a frustration for Sauron rather than a weakness for the Elves, and I think this is why he invested so much effort in trying to recover the One, which would instantly have made all of his enemies' designs moot. Otherwise he would have had to have expended great time and effort in concentrating his power in the North and hoping to deal with the Elves piecemeal, which may have required more patience than that of which he was capable.