If one were to buy and hold solid avaerge coins (not a coin that kicks out and gets 10000% gain), but rather a nice steady gain like eth, Ltc etc (top 20) and starts with 10k, is it possible to reach a million without trading and buying/selling at highs and lows? If so, how long would you predict it would take? Or are most coins not going to last long term, so every 6 months would I have to rebalance with newer coins?
Yes, you can just buy bitcoin now, and wait until it reaches
1 000 000 USD. You need
3 - 5 years of Hodling, and that is it.
This thing just started, less then 1% of world population are involved in crypto, some 20 - 25% are in denial phase ( primary phase of consideration ), and probably 50% of world population isn't even aware of crypto.
So the price of BTC is now 11 000 USD, what would be the price on 20% of global population involved? And they will come, don't worry. If nothing bad happens to us, they will come, for sure.
For your second question, ... if you buy new coins, no one can guarantee you how long will they last. But there are coins out there which are already several years old, so I would personally choose that kind of coins.