Nothing wrong with using a trailer in these circumstances.
I do most of my longer touring with panniers, but have three trailers (and don't own an automobile). The issues will depend a bit on the particular trailer. For example,
One of my trailers is a Burley Travoy. This is my grocery cart/trailer and it does fine at that purpose. However, I wouldn't bring it on a tour and there are a few issues:
- It is a two-wheel trailer, so there are now three wheels to track. Not a big deal if the road is wide and smooth, but add some potholes or glass to avoid and it becomes more tricky.
- This particular trailer attaches at the seat post, that type of higher attachment might be slightly less stable than if it attached down low.
I also have a Bob trailer that I use for carrying larger amounts of stuff. The advantages/disadvantages of touring with this include:
- It carries a lot of stuff. Good if this is what you want to do, but you do want to be careful on accidentally overpacking too much simply because you can
- The rear wheel is a different size than the other wheels, so I have to be prepared to patch/fix two different wheel sizes.
My third trailer is the one I've toured with a few times and is my preference from perspective of touring. It is an extrawheel trailer which is slightly different than my Bob in a few regards: it has a the same wheel size as my bike, so no separate tires/tubes or similar issues. It also tracks remarkably well even better than the Bob.
- The largest downside might be if I need to carry my bike over logs or similar off-road obstacles, I find it more awkward than just the bike alone.
- It is also one additional thing I need to take with me if I am flying in an airplane.
Handling with pulling a trailer is sometimes slightly different, but I get used to that pretty quickly. Overall in similar circumstances where the bike might not support panniers, I would use a trailer instead.