High heat input can create a strong join while weakening the steel adjacent to the weld. The softened metal to each side of the weld loses tensile strength. Ultimately, this means that while you may have achieved a good weld, you may have weakened the overall strength of the material.
What specific type of steel were you using? What alloy in the sticks? What was your travel speed? Weld size? Steel thickness and condition, hardness, notch toughness? Cooling rate? Quenching? All of these variables and more play a part in weld strength.
Ultimately though, I'm not going to say you're "wrong". Experience goes a long way, so do talent, skill and intelligence. After years of learning and doing, I think one develops a "feel" for it. I know I don't use a formula to determine the perfect combination of heat, travel speed etc before I start welding (and the formulas
do exist; welding is a complex science.)
All that said, I am
not a professional welder. I am a sculptor who knows a bit about welding. In the end, it is best to err on the side of caution, especially when welding something that travels at high speed, has no shock absorption capacity, and vibrates like mad.
There are young people full of their own sense of immortality out there who are taking up welding for the first time to weld
two halves of a bike together. There are members of this forum who have little riding and welding experience who are welding their frame and to top it all off are buying non-DOT approved Biltwell
novelty helmets because the style goes well with their bike...
The truth is though, that it's entirely up to them to put themselves at risk. I do it nearly every time I'm on a bike. I ride without a helmet and drive too fast, but I do it with full knowledge of the risk and do everything I can to minimize the chances of injuring other people. So, personal risk is not what really concerns me.
What happens when the hobbyist becomes bored with the current bike, or needs the cash and decides to sell it? Will they warn the buyer that the frame was welded together in their garage by someone who has no welding certification at all, and no real experience? Or will they forget to mention it, or decide not to tell them so they can get the highest price? Will they let that person drive off, unaware of the potential for death or worse? (Because in a bike accident there is definitely worse.)
OK, soapbox aside; have your frame welded by a pro.