I just ran a couple teching strats on express to try them out, both to moderate success. However I have struggled to find the right ballance between growing fast early in the set, vs taking advantage of prices that are much higher. Anyone with experience that can help me think through that decision.

Obviously you can only make money as a techer by not growing. However the more you grow early the more productive you are later. But the tech prices are often 250% higher early in the set. I seem to struggle with this the most between turns 400 and 700.

The right balance is to only tech enough for maintaining growth, unless you will make more money per turn at the small size than you will once you reach stockpiling size.

If tech prices are 2k by the time you reach your stockpiling size of 18k acres (with 6k tpt), then you need to be making 12 million per turn on the tech you produce at a small size for it to be wiser to tech turns for surplus cash.

If you are not making more money teching early on than you would once you reach stockpiling size, then you should be teching only to fund the military and buildings you need, and nothing more.

It's not that straightforward:
1)The larger you grow the less turns you have to stockpile.
2)The larger you grow the more upfront cost you have in terms of building costs, land upkeep and your tech points are less effective
3)There is a fixed demand for tech on the market so the larger you get the more your production will erode the market prices.

The more I think about this the more I believe that as a techer you need to stop growing earlier than almost any other strategy.

I would say 3) is wrong; (at least in alliance, and therefore probably express?) it should peak mid-set i'd think in express, the demand..

1) That's correct. But you should have an estimate before you start the country of what landsize you will aim for and what day you will reach it.

2) That is not relevant. Your production funds your building costs, not your stockpile. Your land upkeep is meaningless because its so small. And the effectiveness of your tech points is irrelevant because it has no effect on your production.

3) There is not a fixed demand for tech on the market. Demand varies as the set goes on, as different countries go through different phases in their growth. No one country is large enough to have a noticeable effect on market prices in the high demand techs.

A techer does need to stop growing earlier than any other strategy. All other strategies have production while growing (with the exception of TMBR, which does not produce while growing, but unlike techer does not sacrifice production to grow, either). Therefore, growth hurts the income of a techer much more than it hurts the income of any other strategy. Additionally, tech prices are on a natural decline all set. The only ones hit harder by a decline in prices are indies and MBRs. Farmers see increased prices as the set goes on, up until people start destocking, and cashers see an increase in buying power (due to a decrease in military and tech prices, and only a slight increase in food prices) as the set goes on.