The comments on your question seem correct to me - that the word "ever" is used to enhance the meaning of "since".
There are some distinctions I would make:
Ever since that day, he has been like a different person.
This implies that something happened on that day that changed him, and he has been acting differently every day, consistently, between then and now.
Since that day, he has become a different person.
With "since", and no "ever", I can write a sentence that implies that he has changed somehow between then and now, but I don't say when. He could have changed three days after "that day", or it could have been yesterday. (This sentence also implies that the change happened because of some reason unrelated to "that day".)
Additionally, the word "ever" can be used to differentiate "since" from its other meaning, as a synonym for "because". Consider:
Since she started wearing purple, he has been wearing blue.
This could mean either that he started wearing blue because she started wearing purple, or that he started wearing blue after she started wearing purple, for reasons unconnected.
Ever since she started wearing purple, he has been wearing blue.
This sentence can only have the second meaning - that his wearing blue started after her wearing purple, but not necessarily as a result of it.
I can give you a British English definition as I own such vehicles...
A caravan is a trailer towed by a car:
A camper van (or campervan) is a van of ~1 ton converted for sleeping & cooking. These are typically VW Transporters or Mazda Bongos. There are still huge numbers of lovingly preserved VW campervans on the roads (I have a classic T2 and a T5):
A Motorhome is a purpose built vehicle, larger than a campervan. These are coachbuilt onto a commercial chassis. The chassis are usually Peugeot or Fiat. They come in varying sizes but are rarely more than 3tons:
You will find people "in the scene" who get very picky about how their vehicles are described. Some people will get upset if you refer to their motorhome as a camper for example.
We British do recognise the term RV as being an American equivalent. However, in Britain, when applied to British vehicles, the term is usually only used for the very large:
Best Answer
In terms of the information a listener would extract I don't think that there is much, if any, practical difference between the two.
Grammatically, the first example uses the present perfect tense, in which making the decision [to watch the show] occurred at an unspecified point in the past and may still have relevance in the present. The second example uses the past indicative tense but does not specify a point in time any more than the first example and does not suggest direct relevance to the present.
I personally would prefer the first example in cases where I am still watching the show or otherwise currently engaging with it in some way, and the second in a case where I've watched every episode and no longer engage with the show in any way. However, if I were trying to express those ideas I would not rely on verb tense alone like this to convey my meaning.