Can you give me a tip how to deal with the new support item mechanic?

Now that Sightstone and the level 3 support items have been merged, there's a problem I frequently run into...

When I finish the third level support item, say Remnant of the Watchers, the quest is usually just not quite done yet, maybe at 460-475 of the required 500. Hence purchasing that item doesn't do a lot for me in terms of vision, since it has 0 stacks. And even if I complete the quest shortly after, it only contains one ward, not all four, so I need to back once more. That is, this item always forces me to either stay in lane until I have completed the quest before recalling to purchase it (which is unfavorable because I need to stay out when everyone else has recalled), or I need to (otherwise unnecessarily) recall a second time once it completes, when I don't have a lot of gold or low hp or mana...

It feels like an ill-behaved mechanic to make the support recall for his central primary item to work properly. I mean, my mid laner doesn't have to recall to enable Seraph's Embrace's shielding active, nor does my ADC before the Muramana passive is enabled. So why do I have to? It feels so unfair -- everyone can choose his back timings based upon sensible values like gold, health or mana, but not me... As a support, I'm anyway starved from Gold and XP, and yet I need to waste another minute for an addition recall cycle.

But maybe I'm doing it wrong? Should I wait with the purchase until after I completed the quest? Should I stay in lane? Or am I just too passive in lane and need to try to get the quest completed earlier by going into trades more often for Spell Thieve stacks or Coin procs?

I wish completing the quest at least reset the trinket cooldown, so I get at least some vision value out of it.