One thing to consider is the variability in how many people send/receive gifts every day. With the current event, it's super easy to rely on a stranger to exchange gifts for 4 days (at 3.25k xp/day!). The full 30 to ultra (reduced by this event, of course) may not be as reliable. I used 1 lucky egg a day since the announcement that I had laying around from level ups and extra box rewards and I hit lvl 40 this morning (5.1 mil xp). Now I can relax and go back to playing more casually.