Given that logery is a 1/6 chance of showing up and there are 4 refreshes a day. You can get an average of about 3.3shards a day with no refreshes. That's about 84 days to go from 3 star to 7 star if you have the currency and don't miss any. About the same as a hard node with no refreshes. Though slightly better since you get 3.3 shards a day rather than 2.6.
And like hard nodes, crystals can speed this up. For 200 crystals a day you can cut that in half.
So if you are at 3 stars and you want to make it, you probably have to spend some crystals. Though if you played the ewok event any, you probably have a star or two from that. So with focus it is possible.
But it's also possible to do it without logery.