Skyrim – Time Required for Dragon Resurrection

I've completed the game and all factions with a level 51 Khajiit archer and didn't notice any significant increase in the number of dragon attacks at any particular point in the storyline. I am attacked perhaps once every 2-3 in-game days. In your circumstances, I would suggest adapting your character to deal with the increased attack rate and develop a few evasive procedures. Some ideas:

• You already have Dragonrend. By forcing the dragon to land, you are able to kill them more easily or force them to fall behind if you wish to escape.

• Take potions of fire and frost resistance to reduce the damage the dragon is able to deal, potions of healing to negate that damage, potions of stamina to help you put distance between yourself and the dragon if necessary, and potions of fortify one-handed/two-handed/archery/destruction to help you deal more damage.

• Hire a companion with high health that engages the dragon in melee or ranged combat. Optionally also seek out Shadowmere from the Dark Brotherhood questline. By having one or two tanks to absorb damage and distract the dragon, you will be free to fight or escape at leisure.

• Attack the dragon from the side, targeting the wings. The tail attack can stagger you, and the head attack can one-hit kill you. The wings deal less damage comparatively.

• If you need to escape, aim to run through a forest or an area with a significant number of large objects covering the ground. The dragon, unable to land, will attempt to deliver one or two aerial attacks before locating the nearest wild animal, hunter or guard and get distracted by it. By using Dragonrend, you can force it to seek an area to land, often a fair distance away.

• Sell the dragon bones and scales, or craft armour from them. The profits will offset the cost of fighting the dragons. By accepting the dragon hunter bounties from the local Jarls, you will get extra coin for eliminating dragons and ensuring a dragon-free Skyrim.

From what I see here it looks like 18 are learned without requiring dragon souls, though I'm extrapolating a bit since I haven't reached the end of the main quest yet, myself.

Fuzzy math:

Animal Allegiance     3 Souls    
Aura Whisper          3 Souls    
Become Ethereal       3 Souls
Call Dragon           0 Souls* 
*I'm making the assumption that this works a bit like Unrelenting Force
Call of Valor         0 Souls
Clear Skies           0 Souls
Disarm                3 Souls
Dismay                3 Souls
Dragonrend            0 Souls
Elemental Fury        3 Souls
Fire Breath           2 Souls
Frost Breath          3 Souls
Ice Form              3 Souls
Kyne's Peace          3 Souls
Marked for Death      3 Souls
Slow Time             3 Souls
Storm Call            3 Souls
Throw Voice           3 Souls
Unrelenting Force     1 Soul
Whirlwind Sprint      2 Souls

So...3+3+3+0+0+0+3+3+0+3+2+3+3+3+3+3+3+3+1+2 = 44