The ability to row in any conditions, raging crosswind, two-foot tall jet ski wakes, torrential downpour, is absolutely essential in order to be a champion sculler. It all comes under the heading of boatmanship. Some races are won on nothing more than superior boatmanship.
If you want to be your best, spend a lot of time exploring what is more than enough. Push yourself until the bar is lying immobile across your chest. Push yourself right off the edge of your capacity.
Long live the elite rower's motto:'early to bed, early to rise, never meet the regular guys.'
As you become more proficient, fewer people can offer you advice, although in truth, that's when you need it the most because the stakes just keep getting higher and higher.
One training device is the ergometer. I never owned one, never trained on one, and practically never used one. The few national team tests I took on ergs were dismal failures, which worked wonders to further my dislike of these beastly creatures. Boring. Tedious. Noisy. Ergs have greatly cheapened rowing. Graceless. Greasy. Grim. The erg is to rowing what having sex by yourself is to having sex. Stop it!
You need flawless balance on the recovery. You need white hot focus and the concentration to row square blades cleanly for seven miles. Smooth water doesn't hurt either.