1 Only so much/many, Only so long
These adverbs express a limit to an action or to a quantity. This means that the action cannot continue forever or that the quantity can no longer be increased. Thus, we say that something cannot go on and is probably coming to an end. However, we do NOT estimate when this end might occur.
For example: I can only be here for so long.
Only so much/many
We use the word much or many with the phrase only so, depending on the noun countability that follows.
Let’s look at some examples:
→ I can only eat so much food.
We say that there is a limit to how much we can eat before it becomes impossible to eat any more. The noun food is uncountable, so we use the word much.
→ You can put only so many balls into the bucket.
We say that the bucket is not bottomless so there is a limit on how many balls it can fit into it. The noun ball is countable, so we use the word many.
Only so long
The phrase only so long is used when we want to express a time limit for an action.
→ Their relationship can only last for so long.
We show that the relationship has no future and is likely to fall apart soon. But we do not say when this might happen.
More phrases with only so
We can use other adverbs with only so. For example, far etc.
→ I can only run so far.
Probably we are limited by our physical condition and therefore we cannot continue running.
The phrases Only so much / many, Only so long are rather “linguistic blubber” but are used quite often. In addition, if you use them correctly, your English will sound more elegant.