Charging

How long is "too long"? The charging rate inherently slows down once it reaches 80%. I can be more noticeable if you use a more powerful power adapter, as it may charge quickly to 80% before the charge rate is severely reduced. It's needed for various safety/longevity reasons.

Batteries - Why Lithium-ion? - Apple

It charges fast for convenience and slow for longevity.

Your Apple lithium-ion battery uses fast charging to quickly reach 80% of its capacity, then switches to slower trickle charging. The amount of time it takes to reach that first 80% will vary depending on your settings and which device you’re charging. Software may limit charging above 80% when the recommended battery temperatures are exceeded. This combined process not only lets you get out and about sooner, it also extends the lifespan of your battery.

What are you using as the power supply?

What iPhone? 7 hours seems excessive. For an iPhone 7 and a 2.1A power supply it should be somewhere around 1 hour to 80% and maybe another hour to top off to 100%.