Don't worry about the failure... 8 is a lot.. 1 is no worry for a beginner and let's just leave it at that.
I don't buy the "heat" thing... It's a technique thing.
A 3/8" limited thickness plate of A36 base metal cant really be overheated with SMAW even if you make the next pass directly chipping and brushing the previous pass all the way out. A one minute pause between passes and cleaning should be perfectly fine. A36 is not going to get hard or soft because of SMAW welds being quickly placed... It just won't.
If you are running your 1/8" E7018 at 120 amps or less on the verticals I seriously doubt that the top of the plate is going to get so hot that the puddle is hard to control due to rising heat up the plate... The loss of control happens with change in rod angle, as your rod angle becomes more steep (twisting your wrist instead of lifting your arm) the puddle gets longer and more teardrop shaped instead of nice and round..(((YOU CAN SEE THIS))) It's not overheating .... It's technique.
Having said that... This technique issue is a problem that pretty much every beginner goes through... And some experienced welders too. Think of the perfect rod angle when you start..... When you get about 2/3 of the way up the plate, think again about that rod angle, to make sure you are keeping it right.
As a biginner you get stressed out about thinking all these things... Rod angle, Arc length, Travel Speed, watching it all at once and making adjustments.... The good news is that much of this will become automatic,,, You will get used to seeing these things and adjusting without thinking much about it... Experience...
I bet you do fine.
Vertical uphill progression using 1/8-inch diameter E7028:
Most welders try to use the lower end of the amperage range and fight the arc all the way. Turn up the amperage to around 135. Keep a short arc. Weaving is fine unless the WPS is qualified for CVN and the heat input is limited. When weaving, hold the corners to permit the weld to fill and avoid undercutting the edges.
When you set up the plate assembly, tack weld the bottom and the top of the plates to avoid magnetic arc blow as you approach the uppermost two inches. "Grounding" the test plates both top and bottom reduces the current through each tack and reduces the magnitude of the magnetic field that causes the arc blow. Position the plate assembly between your belt buckle and sternum. You are less likely to roll your wrist and change the rod angle, which by the way, should be about 15 degree upward.
Good luck and practice, practice, practice.
Merry Christmas - Al