Fiberglass poles are inert objects. Their chemistry doesn't change as they get older or get used. They're ELASTIC, meaning that they spring back to their original shape when bent out of shape. So no, there's no such thing as "breaking in
" a pole.
Even in hot weather, poles don't bend more. It's just that the vaulter is more warmed up, so his warm muscles allow him to run faster - giving the ILLUSION that the pole bends more in hot weather.
A pole's flexibility has these variables:
Weight (in increments of 5 pounds)
Length (in increments of 6 inches)
Flex (flex is measured differently by each mfr)
The flex is only important to distinguish between poles of the same weight and length. Since pole weights are manufactured and rated in increments of 5 pounds, you could (roughly) think of the various flexes for a pole of a certain weight as being between 1-4 pounds lighter or heavier than a pole with an average flex for that weight rating. The higher the flex, the stiffer the pole. But let's disregard that detail for now.
How much the pole bends has to do with your grip, speed, and technique. I would guess that your technique needs some improvement, but your first step is to understand the RELATIVE differences in weight between the poles you've been trying.
Refer to Jan Johnson's pole chart for this, at: http://www.vstraining.com/skyjumpers/component/content/article/93-articles/pole-vault/65-pole-progression-chart
From that chart, here's some of the poles in the range that you're discussing:
32. 13' 155
34. 13'6" 155
34. 13' 165
35. 13' 170
36. 13'6" 165
36. 14' 155
37. 13'6" 170
38. 14' 165
39. 14' 170
Poles on the same line bend about the same amount (within 5 pounds of each other, depending on their flexes). Poles one line apart are about 5 pounds different (despite the weight marked on the pole).
So a 13'6" 155 is about the same weight as a 13' 165. And a 13'6" 165 is about the same weight as a 14' 155.
You say that on a 13'6" 155 (which is on line 34) you say you bend it OK (raising your grip to 13'6"), but it breaks the HS weight rule. For a better comparison, you might want to try this pole with a 13' grip, and see how it feels. But be careful - it's even lighter than the 13' 170 which you say is already getting too much bend. If you had identical technique and grip on these two poles, you should be over-bending this one even more than the 13' 170! I question whether you actually cleared a reasonable bar with the 13'6 155 (with full inversion), or did you just bend it and then bail?
And you get too much bend on the 13' 170 (which is on line 35) when you grip at 13'.
On a 14' 170 (which is on line 39) you don't get any bend when you grip at 13'.
If you compare these 3 poles, you'll see that there's something strange going on. It's probably your technique. Maybe you panic and vault differently with a stiffer pole?
Assuming that you can handle a grip of 13'6", and you need at least a 165 to pass the HS weight rule, the softest pole you could choose would be a 13'6" 165. That's on line 36. That would be only 5 pounds heavier than the 13' 170 that you're over-bending, but 15 pounds lighter than the 14' 170 that you can't bend. So that would be a good choice.
After the 13'6" 165, the next pole up would be from the ones on line 37. But on that line, only the 13'6" 170 matches your minimum length and weight.
Next up after that would be on line 38 - either the 13'6" 175 or the 14' 165.
Conclusion: Don't jump up so many pounds in relative weight. Instead, go up in as small of increments as you can (assuming there's no pole availability or cost barriers).
But read my next post too.