AWS RDS instance upgrade down time

I have a few questions in regards to upgrading the RDS instance.

1. What is the downtime when upgrading the instance from let's say small to large. Is the downtime relatively similar when you go and change any instance type(small, large, xlarge) or are there determining factors such as database size that alter the timing.
2. Can anyone share a technique of how to upgrade the instance type avoiding the downtime using RDS? Is that even possible in RDS. It doesn't have to be in great detail just some cliff-notes/big-picture stuff.
3. Is there down time when you allocate more disk space?

I don't think this is an on-topic question for StackOverflow at all, but some information anyway:

1. It's significant and depends on the size of the database. I've had it take an hour or more some times. I've also had creating snapshots, restoring from snapshots, and multi-az creation take around two hours before.

2. It depends on how you have things configured now. If you have Multi-AZ already enabled, then an instance upgrade will actually occur on the slave, then a failover will occur, then the new slave is updated. This results in about 1 or 2 minutes of actual downtime. The instance upgrade on the slave usually takes around 10 to 20 minutes, but there is no downtime in this setup. Note that when it does the failover, Amazon does a DNS swap internally so that your RDS endpoint points to the right machine, so you may have to restart your web processes that point to the DB so that they reconnect to the DB and pull in the new IP from a new DNS lookup.

db.t1.micro > db.m1.small : 8m30s

Engine:    mysql
Storage:    6GiB
Backups:    Yes
Multi A-Z:  No

The size/type of the database do appear to affect the downtime significantly.

1, From personal experience it takes just short of one hour, to be precise 57min for 15 GB instance goign from small to large. Which I did not expect to be that long to be honest. update: just learned that switching point in time backup before upgrade speeds up the process significantly

2, I would say creating MULTI AZ before doing upgrade would do the trick, hopefully that does not have downtime as well. Question is do they allow upgrading one without other...

3, yes, but I'm not 100% sure though