Since you've already gotten a rare from Sage Treasure, save the rest of your seals for Kage Treasure.

Oh, my bad, I read that wrong.

In that case, I would use around 40-70 seals to get a rare from Sage Treasure, but ONLY if you need one of the 3, and then I would save the rest of the seals for Kage Treasure.

I don't have any of the Pains and have been doing pretty well thus far.

Once I got Sage Naruto, however, everything changed. Pulling from Sage Treasure is totally worth it 100% of the time.

So even without any of the rares from Tendo Treasure, you can still do pretty well. But it's up to you.