Hi Yuechu,
Like Gonecar mentioned, the 来 or 以来 at the end of some time phrases usually means up to this time (of speaking).
However, it needs to be pointed out that using this type of time phrases usually means the expresser intends to express a result after all that happened during the period (rather than to express something that happened during the period). Therefore, the grammatically correct tense in the main clause should be a perfect tense.
In Chinese, 过 is used to indicate perfect tenses while 了 is used to indicate past tenses. Thus, I would suggest using 过 instead of 了 in the examples above, as follows.
这么多年(来),我们只见过一面。 For so many years, we have met only once.
这么多年(来),我只见过他一面。 For so many years, I have met him only once.
这么多年(来),我们连一面都没见过。 For so many years, we haven't met even once.
这么多年(来),我一直在找他。 For so many years, I have been looking for him. (一直 is usually used to express perfect continuous tenses.)
If you intend to express something that happened during the period, you may simply change 这么多年(来) to 这么多年(里), i.e. in so many years. For instance,
这么多年(里),我们只见了一面。 In so many years, we only met once.
这么多年(里),我只见了他一面。 In so many years, I only met him once.
这么多年(里),我们都没见(了)。 In so many years, we didn't meet.
这么多年(里),我都在找他(了)。 In so many years, I was looking for him.
The difference between 我一直在找他 and 我都在找他了 is that
我一直在找他 tends to infer a result that I'm still looking for him or perhaps that I finally found him just now.
我都在找他了 tends to infer that I spent a lot of time in looking for him rather than in doing other things.
As you may note, both 这么多年来 and 这么多年里 may be abbreviated as 这么多年. (这么多年里 is abbreviated more often.) Hence, the tense in a sentence with 这么多年 may be a past tense or a perfect tense. That is why both sound understandable for a native speaker, but they actually emphasize totally different points.
I wouldn't suggest you spend much time in understanding the logics in Chinese grammars (in order to translate between Chinese and an other language in a grammatically equivalent way) because Chinese grammars are not so systematic and strict as most of other languages'. I would suggest you spend more time in imitating how native speakers express idiomatically and in learning how they understand (guess) the meaning of an ambiguous expression based on specific circumstances.