If you have built Oxford and switched to representation, you are already in the late middle game. If you have a great person in 400BC it may be nice to know that the settling option will eventually give 18 or 27 bpt, but the decision as to whether to settle, light-bulb or start a GA will not be greatly influenced by the impact many turns in the future. What to do with a Great Person in 400BC is a very different question from what to do with one in AD 1500.
RJM
I disagree, knowing that the benefit keeps going up to scale with higher tech costs later has a great impact on deciding whether to settle.
Also, AD 1500 is very, very late for Oxford. If you don't think you'll have it built until then, it is more likely better to skip the specialist, hence, the value of planning ahead.
These are all excellent points and they STILL don't highlight everything

. You also have to factor in the turns of actually getting oxford built sooner, having free speech/emancipation/US or other civics longer, etc etc. We've also left trades out of this so far. If getting a bulbed tech faster means trading it with more AIs, it further skews it in favor of bulbing. Trades are the greatest "beaker multiplier" in the game oftentimes."
This statement works under several assumptions:
1. At the point at which you bulb education, you will have enough strong production cities to build universities for Oxford straight away. This is not always the case. Sometimes it is better to build forges or other cheaper buildings first, or you just have to grow a bit, and it ends up being the case that bulbing education did NOT really get you Oxford any sooner. If you already have a burgeoning empire, then yes, in that case you'd want to bulb because you know you can get Oxford up straight away.
2. Same applies with Universal Suffrage. It is not always the case that you want to switch to it so soon, because
1. You may not have many towns
2. You may not have enough happiness
3. You may want to keep the higher research rate from representation.
And the same applies to free speech. Bureaucracy can be better than Free Speech from an economical standpoint for a long time. But again, if you have a large empire rather than a small one, it is almost always the case that rushing to a benefit that applies to the WHOLE empire outweighs a static bonus of 27 beakers per turn(well, 18 probably since it seems you want to run US, which makes the settled GS even less appealing). That is the assumption that seems to be being worked upon here.
If you are going for a cultural victory, then getting Liberalism faster is better. That's a different case.
But, I will agree, the power of trading makes bulbing most often the superior choice because you bulb for essentially 3000+ beakers, not the normal 1500. The settled great scientist more often has viability if you know you will get enough great scientists that you will run out of good trade bulbs, or if you are in a different type of game, for example, isolated, tech trading off, etc.